MAJOR AIR DISASTERS: ACCIDENT INVESTIGATION AS A TOOL FOR DEFINING ERAS IN COMMERCIAL AVIATION SAFETY CULTURE

. The air transport evolution has been littered with major air disasters, the occurrence of which has not only had the negative effects inherent to any disaster. Air accident investigation has provided a wealth of knowledge that has advanced the aviation industry and its safety. International Civil Aviation Organization has exercised international regulatory leadership since 1947, developing tools with international cooperation, such as the air accident investigation methodology. ICAO has forged a change in perspective on safety attributions or factors in different historical eras, using this methodology to deepen the understanding of the causes and thereby achieve aviation safety improvement. Authors aimed to analyze, through a detailed study of the world’s worst aviation accidents, their contribution to understanding the details of aviation safety culture. Beyond the technical issues and fatality rates, the necessary analysis is what knowledge researchers have gained from the beginning, exploring the attributions of reports and knowing what diverse factors have predominated in different eras. Descriptive analyzes of air disaster investigation have two objectives: to identify the beginnings of a global safety culture resulting from evolution in operational safety and to relate the different eras to the attributions of air accident investigations.


Introduction
Is safety culture present in commercial aviation worldwide?If so, at what particular time does an efficient safety culture appears in the commercial air transport industry?What technical, human, and organizational factors are characteristic in each of the diverse eras in which aviation safety has historically developed?Before the development of commercial aviation, as it is know nowadays, the Wright brothers marked a historic milestone in 1903 with the first powered flight in history (Bravo, 2016;Bridges, 1967;Burrel, 1992;Hawkes, 1992;Marimón, 1973); however, they were also protagonists of the first fatal plane crash, only a few years later, in 19081 (Bridges, 1967;GTD Engineering System & Software, 2010).This tragic first accident not only led to the evolution of its prototype but also served as a way to learn from its mistakes and caused, in short, an improvement in incipient air safety.These preventive measures came about before it was possible to speak of aviation security as such, before aviation was transformed into a globalized and profitable industry, and even before it became a mass air transport. 2he subsequent development of commercial aviation would not begin until the mid-twentieth century, although since then, the aeronautical industry has experienced exponential growth up to these days.Nevertheless, the evolution of the industry, like the pioneering Wright brothers, has not been accident-free since its inception.The numerous accidents have been caused by several factors, which present different importance depending on the historical era under study.Initially, most of the incidents were due to technical issues, giving way later to the human factor as the main precipitating one, and after the aeronautical industry implemented an endless number of technical improvements.When technological advances reached their maximum development, they generated the need to integrate man into the machine.Finally, a closer look at the last decades of the last century shows how organizational and institutional factors started to appear when the complexity of the industry began to need greater regulation.
This study not only focuses on the search and definition of the beginning of a culture of aviation safety, as it is understood globally in other industries3 (Institute for an Industrial Safety Culture, 2017, 2021) but dives into the history of aviation safety (International Civil Aviation Organization [ICAO], 2006[ICAO], , 2009[ICAO], , 2013a[ICAO], , 2018) ) through the reports on the most relevant accidents that have taken place.Air disasters tell the story of typical learning in a young industry (less than 100 years making its operations profitable) not exempt from certain dangers.The factors revealed have been distributed differently in different eras.Authors such as James Reason, Frank E. Bird, Edwin Edwards, and many others focused their studies on human error.Additionally, they contributed to causing a period of change in mentality that delimits two fundamental eras in the analysis and management of air accidents caused by the human factor.Thus, at the beginning of the 90s, this intersection or change of attribution concerning human error can be located; when it was first openly recognized that the operational context directly influences the performance of the human factor as a generator of incidents and accidents (ICAO, 2009).
A proper way to approach all these issues is to study the original investigation reports of past air accidents, as they represent a vast source of knowledge.To this fact is added that almost all of them are available, and their consultation is publicly accessible.The objective sought with this is to identify the specific beginning of the safety culture.Additionally, demonstrate the factors that have been predominant in every historical era of commercial aviation.The methodology of accident investigation (ICAO, 2001(ICAO, , 2011(ICAO, , 2012(ICAO, , 2015(ICAO, , 2016(ICAO, , 2020a(ICAO, , 2020c) ) has been extensively developed in air transport regulations and is as old as aviation.This development, its leadership, and international unification come from the hand of the International Civil Aviation Organization (ICAO, 2021), a specialized agency of the United Nations in everything related to aviation.

Safety culture and air disasters
Safety culture definition has evolved throughout the different editions of the ICAO Safety Management Manual.The initial editions (ICAO, 2006;ICAO, 2009) considered the terms safety culture and organizational culture as synonyms, referring to share beliefs, practices and attitudes.The third edition used the term organizational culture adapted to safety and with reference to the characteristics and safety perceptions among members interacting within a particular entity (ICAO, 2013a).In the latest edition, the definition links the operational safety with the human factor in the aviation system as how people behave in relation to safety and risk when no one is watching, which coincides with that used by the Institute for Industrial Safety Culture ([ICSI], 2021).Therefore, the definition is becoming universal and global.It is then that ICAO recommends accident investigation as a basic tool and methodology to analyze the real evolution of safety culture (ICAO, 2018), and does so under Article 37 of the Chicago Convention on Adoption of International Standards and Procedures "Aircraft in distress and investigation of accident" (ICAO, 1944, paragraph k).
Accident investigation is a post-accident analytical technique that can also serve as a reactive method of prevention (Rodríguez, 2012).This technique has been and is one of the pillars for the development of security in general.In the field of air transport, it has been of vital importance in the prevention of accidents, creating and promoting improvements in the design and manufacture of aircraft, training of personnel, protocols and in the development of extensive legislation.Investigations into major air disasters have promoted both reactive measures (recommendations) and preventive measures (increasingly complex global improvement system) (Lombardo, 2020).
Commercial aviation has proven to be able to evolve, acquiring knowledge from the investigation of its accidents.Furthermore, it has succeeded in integrating and managing this knowledge with high levels of operational safety, enough to guarantee the economic profitability of the sector.Regulatory leadership as a generator of safety culture is vital to understanding this evolution.ICAO has created a common language, internationally standardized management system processes, and generated policies, regulations, and manuals to increase the safety of operations.It could be argued that one of the most important contributions (technical, human, and organizational) that have marked the safety culture is the investigation of technical, human, and organizational errors in a high number of accidents (ICAO, 2018).
The most catastrophic plane crash in history, in terms of fatalities, was the one that occurred, in 1977, at the airport of Los Rodeos (Tenerife, Spain), in which two Boeing 747 collided, with a fatal balance of 583 deaths (BBC Mundo, 2013;Helmreich, 2006;Ranter, 2015).The principal cause was the unauthorized take-off of the pilot of one of the aircraft operated by KLM (Koninklijke Luchtvaart Maatschappij).However, its technical analysis shows how an innumerable chain of events and technical, human, and organizational errors contributed to the outcome.Firstly, the bomb warning at Las Palmas airport caused the diversion of all flights to the nearby Tenerife Norte airport -Los Rodeos-, which also had only one runway, without ground radar and damaged runway lights.Secondly, the appearance of very dense fog and the presence in Los Rodeos tower of only two air traffic controllers, absolutely overwhelmed by the excessive traffic of that day at the airport.Finally, the linguistic confusion and cancellation in radio communications, the rush syndrome, the lack of recent flight hours of the KLM pilot, and the organizational pressure of the policies of the operator of that company formed the perfect combination for the disaster.As the only positive aspect, we can stay with the fact that the subsequent investigation into this accident would cause substantial changes in international regulations and dozens of recommendations for air operation (ICAO, 2013b).Before Los Rodeos, the airlines modified the training for pilots in command, creating the management of resources in the cabin (Crew Resource Management [CRM]), which has continued in constant evolution (Muñoz-Marrón, 2018).Airlines also created awareness of the problem of the hierarchy in the cabin (Comisión Investigación de Accidentes e Incidentes de Aviación Civil España, 1977).
Accident and catastrophe are different terms.The Royal Spanish Academy of Languages (RAE) differentiates between an accident "eventual event or action that results in involuntary damage to people or things" (RAE, 2020a, definition 2), and a catastrophe "event that produces great destruction or damage" (RAE, 2020b, definition 1).The World Health Organization (WHO) also adds an aspect related to the risk process by defining catastrophe or disaster in English as a "serious disturbance of the functioning of a community or society that causes widespread human, material, economic or environmental losses that exceed the capacity of the affected community or society to cope with the situation with its own resources" (World Health Organization, 2008, p. 22).That is, catastrophe not only as a result of a natural hazard, but as a risk process in which several elements appear (the existence of a danger, vulnerability and insufficient measures).In air transport there is no definition of the term catastrophe, but the WHO definition complies with both definitions, both that given by the RAE, and the definition internationally institutionalized by the WHO: Inherent danger of flying; vulnerability that entails a means of air transport and insufficient measures of the technical, human or organizational type, that cause a serious disturbance of the system producing human losses and great destruction.
Understanding that a catastrophe goes far beyond an accident and that there is no definition or aeronautical term to define it, it is important to delimit the parameters on which the industry bases to differentiate the "catastrophe" from the plane crash.It is crucial to be clear about which accidents are considered air disasters to understand how these have driven research and the construction of a culture of operational safety in the air transport industry.The definition of serious air disaster used throughout this paper is limited to the definition contained in the ICAO regulation: commercial flight accidents (general aviation, military, helicopters, and Remotely Piloted Aircraft System [RPAS] excluded), where the aircraft is economically unrecoverable or of the hull loss type4 (excluding fatal type accidents).Excluded too are kidnappings and sabotage due to the unexpected nature of the event and the lack of relationship with operational safety (safety management), and since they are more linked to the physical security measures at airports (security).These measures are adopted to avoid the intentional damage of some people against others whose regulation, contained in Annex 17 of the safety of the ICAO (ICAO, 2020b), is periodically amended in response to evolving threats.

Periods in the evolution of operational safety
It is essential to analyze the different periods and times through which air transport has passed, what normative publications and technical advances have occurred in each of them, and what objectives have been priorities.The rules and regulations that have been necessary to formulate since the creation of the ICAO (in 1947) in its objective to guarantee flight safety are also important issues to consider.The establishment of the structure of this timeline is crucial, as it will delimit the periods of evolution and changes in mentality in terms of safety while, at the same time, checking the behavior and trend concerning the occurrence of primary air disasters worldwide.In short, it will be the line of argument and the constant that will test the hypotheses.
To establish these periods (Figure 1), has been taken as a reference the structure of ICAO technical publications, specifically the Operational Safety Manual (ICAO, 2006;ICAO, 2009;ICAO, 2013a;ICAO, 2018), using all its editions.This manual is a document that provides guidance and detailed information on international safety standards, best practices, and procedures (ICAO, 2006).

Hypotheses
ICAO Safety Management Manual, 2 nd edition, (ICAO, 2009) delimits two clear periods in terms of the errors produced by the human factor: before and after the early 1990s.This second edition defines a specific time point at which there is a significant change of mentality in relation to the analysis and management of accidents.At the beginning of the 90s, the organization recognized, for the first time, that people work within defined operational contexts.Although previously, scientific literature was available in this regard (related to the influence of a given operative context over performance and execution), it was not until the 90s that the aeronautical world publicly and officially recognized this fact.This milestone marks the beginning of the so-called "era of the organization" in which operational security begins to be seen from a systemic perspective, thus encompassing organizational, human, and technical factors (ICAO, 2009).
Considering that, the present paper aims to test the following hypotheses: Hypothesis 1.The beginning of the safety culture is established in the 90s, coinciding with the beginning of the "institutional era".Therefore, during this period, considerable regulatory development in the number of publications of the four established periods can be expected, together with a drastic reduction in the number of accidents and mortality in commercial aviation.
Hypothesis 2. The attributions about causes and recommendations in the investigation of accidents: ■ H 2.1.There will predominantly be technical type attributions during the technical era.
■ H 2.2.There will predominantly be human type attributions during the human factors era.■ H 2.3.There will predominantly be organizational type attributions during the institutional era/total system era.Hypothesis 3. From 1949 to 2020, technical factors or errors will follow a decreasing trend, while both human and organizational factors will follow an increasing trend.

Method
The objective of this analytical-observational study is to identify the specific period where an efficient safety culture appears through a detailed analysis of the literature and existing data.In addition, based on the accident investigation reports, this work tries to find the relationship between each of the established reference periods (as far as operational safety evolution is concerned) and the attribution of the causes of air accidents that occurred in each of them.
Two types of variables are used that, functioning as dependent variables (DV), have a direct relationship with the object of study: ■ Qualitative variables: (1) the accident attribution of causality in the investigation reports.The data collected for both sets of variables (quantitative and qualitative) were analysed using each reference period as a time frame.The analysis of the results provided by the quantitative variables serves to identify, in a concrete way, the starting point of the operational safety culture in each of the eras.
ICAO publications have been chosen as a frame of reference because ICAO is one of the most important regulatory bodies in the aviation sector worldwide.ICAO has always created its own regulatory standards, adapting to the evolution of the sector.A constantly changing and increasingly complex sector that has been able to take on the challenges posed by major air disasters, using them as a learning and knowledge tool to increase safety culture.The number of ICAO regulatory publications (quantitative variable 1) is in the line with the number of changes in operational safety, and is one way of determining safety culture in terms of its importance in generating a shared ways of doing and thinking (ICSI, 2021).
The rest of the statistics rates (quantitative variables 2, 3, and 4) have been chosen because they are all considered to be one of the many consequences of poor safety cultures over the years, and inform us about significant changes in the overall trend, in order to provide us with interesting global information to integrate with the qualitative variable.The operational safety aims to reach the utopia of zero accidents and the safety culture changes people's behaviour in order to achieve as few accidents as possible, because safety culture and the quest for zero air accidents are closely related.
On the other hand, the qualitative variable is used to analyze the relationship between this variable and the types of causality attributions of air accidents in the investigation reports for the period 1949-2020.
Air accident investigation reports have been employed for the study of qualitative variables.These reports present a standardized structure since the beginning of commercial aviation (ICAO, 1970(ICAO, , 2020c)), making them an excellent analysis tool.This structure included in the "ICAO Annex 4 -Mandatory content research report according to Annex 13 and relationship with the technical (FT), human (FH) and organizational (FO) factors involved" (ICAO, 2020a(ICAO, , 2020c) ) shows that the essence of the report itself has not changed.And although the attributions included in them are difficult to measure, in order to quantify their analysis objectively, a triple classification of the causes and recommendations contained in these research reports has been made.Thus the categorization aims to identify which of the factors: (1) technical (material safety condition, factors related to airworthiness status of the aircraft, system design, meteorology and navigation systems), ( 2) human (safetyrelated actions or omissions constituting dangerous acts that jeopardize operational safety), or (3) organizational (cultural, economic, organizational, and management activities with direct and indirect influences on aircraft operation, such as resources and financial viability, management policies and practices, communications, certification safety oversight and regulatory framework, etc.), can be attributed to the occurrence of each of the accidents analyzed.

Procedure
Two types of analysis have therefore been developed.The first is descriptive concerning quantitative variables to test hypothesis 1.The second is through the qualitative analysis of the historical attributions of significant accidents to test hypotheses 2 and 3.
As for the quantitative descriptive analysis corresponding to hypothesis 1, the safety culture eras of evolution differ in the number of years: 21 years for the technical, human and institutional factors, and 9 years for the total system era.The annual average, which facilitates comparison between periods, is used for each variable to unify and compare the results.In addition, to conclude if the jump from one era to another is significant, three Stevens' t-tests (bidirectional and assuming unequal variances) have been performed beyond the graphical representation of each variable.These tests have been completed for each of the three consecutive inter-era jumps (specifically between two eras): technique-human factors, human-institutional and institutional-current factors.This methodology, employed for each quantitative variable of the theoretical model, allows us to check which jump between the eras has statistical significance.Stevens' t-test for two samples is an appropriate method of checking whether the differences observed in the graphical representations are significant.
To test hypothesis 1, about the beginning of the safety culture in the 90s, has been made a count (editions and total amendments during the period 1949-2020) of ICAO publications (Chicago Convention and Annexes from 1 to 19) that regulate international commercial aviation (the two documents on operational safety and accident investigation that develop Annex 13 and 19 have been taken into account respectively and others that significantly comply with the Chicago Convention).Regarding mortality and accident rates, there are few organisms with all the data available, so those provided by the Aviation Safety Network (ASN) database have been used (Ranter & Lujan, 1996).The ASN is a private and independent body that covers accidents and safety issues of commercial, military, and private aviation.
In order to test hypotheses 2 and 3, the conclusions of investigation reports of a sample of accidents that meet the requirements of the definition of major catastrophes framed in commercial aviation have been analyzed, excluding military accidents, general aviation, and hijackings.
To have a uniform sample and thus be able to compare results with respect to the different times, the criterion of choosing the accident with the highest number of fatalities per year between 1949-2020 has been followed.The sample has been extracted from the Aviation Safety Network ASN database (Ranter & Lujan, 1996).From among 23000 records, 71 hull-loss accidents have been selected, the deadliest per year of the period (with more than 49 victims), that is, 21 for each past era: technical era (Figures 2 and 3), human era (Figures 4 and 5), and organizational factors era (Figures 6 and 7) and 8 for total system era (Figure 8) 5 .
From original investigation reports, information on the conclusions of every accident (leading causes, contributing causes, and recommendations) was collected.Once each category is defined, all the sources and recommendations are classified according to one of the three categories.That is, whether they are technical, human, or organizational issues.To provide an example, Figure 9 shows the first four accidents in the sample and their classification according to the procedure described. 5There is no sample in 2017 that meets the established criteria.

Results
The results obtained vary depending on the type of variable.For quantitative variables, annual averages have been calculated (ICAO publications, air accident victims, accidents, and high mortality accidents) for each era.For the qualitative variables corresponding to the attributions, the percentages of the factors (technical, human, and organizational) have been calculated to see how they change, both for each era and the entire period .
The results, in terms of the count of ICAO publications (Table 1), show a more prominent era leap than the rest: specifically, the jump from the technical era to the human factors era.The analysis, carried out through Stevens' t-test, of the average number of publications confirms that this jump does represent a statistically significant increase in the average number of annual publications from the technical period to the human factors (t = 3.32; p < 0.002).The increase, although progressive during the later eras, is not significant, nor is the jump to the institutional era (t = 0.69; p > 0.50), nor that of the jump to the current era (t = 0.52; p > 0.61).
The dispersion by era of total world accident total victims (period 1949-2020) shows (Table 2) a downward trend in recent times.It also places the highest number of deaths, almost thirty thousand, in the human factors era.The highest decline occurs between the institutional stage and the total system one.It is possible to observe two significant periods of change by performing the t-test between the averages of the consecutive eras.The first locates between the era of human factors and the institutional era (t = 2.96; p < 0.005), while the second situates between the institutional era and the present (t = 6.45; p < 0.001).Therefore, it should affirm that from the time of human factors until today, mortality has been decreasing significantly.However, there is no statistical significance between the technical stage and the human factors one (t = 1.82; p > 0.08), although an increase in mortality is observed.

MC -Main Cause, CC -Contributory Cause, R -Recommendation
Factor The total number of accidents per era, during 1949-2020, decreases more uniformly and progressively at the beginning of the institutional era.This trend is maintained in the total system era too.The t-test of averages confirms that the three changes between consecutive eras are statistically significant (t = 2.89; p < 0.01; t = 3.60; p < 0.001 and t = 8.45; p < 0.001, respectively).Regarding the averages in Table 3, it can be observed that the most relevant decline occurs between the institutional era and the current period (total system).
A higher number of accidents in the human factors era can be observed (Table 4), looking at the results of high mortality accidents (those with more than 49 deaths) for each stage, with 184 out of a total of 483 accidents (occurring from 1949 to 2020).The sum of high mortality accidents reflects more accidents in the human factors era, producing its highest decrease during the total system period, starting in 2012 (Table 4).Regarding annual averages, it is posible to find a vast decline in high mortality accidents, especially in the total system era.The t-test between the means of consecutive stages confirms that the only statistically significant drop occurs between the institutional era and the total system era (t = 5.08; p < 0.001).The rest of the jumps between stages are not statistically relevant, nor the increase in high mortality accidents that can be seen between the technical era and the human factors one (t = 1.76; p > 0.086), nor in the decrease between the latter and the institutional period (t = 2.02; p > 0.025).
The descriptive analysis of the quantitative variables shows that hypothesis 1, which places the beginning of the safety culture in the 90s, is only fulfilled and partially concerning mortality (the jump to the total system era is also significant).This analysis shows the most significant jump between eras for all quantitative variables and consequently places an efficient safety culture as of 2011.
Regarding the qualitative variables established for hypotheses 2 and 3, the numerical results corresponding to the 71 accident investigations of the period 1949-2020, which are selected according to the established criteria, offer a total of 1109 causes and recommendations, classified according to technical, human, or organizational factors.They are all listed in Table 5, and their graphical representation by era is presented in Figure 10.
The general analysis of the classification of causes/ recommendations by technical/human/organizational factors of catastrophic accidents of the period 1949-2018 shows (Figure 11) a high percentage of the human factor as responsible both in determining causes (53.5%) and   in contributing causes (41%).After the human factor, the technical is the second type of cause, both in determinants (36%) and in taxpayers (31.3%).Organizational factors are more present as contributing causes (27.6%) than as determinants (8.5%).
Regarding the recommendations of the report, it can be concluded that in the face of human and technical factors as a cause of accidents, the preventive measures issued were of an organizational nature (74.1%).Normative regulation and managerial and institutional control are imposed as recommended main measures in human and technical failures (Figure 12).
Hypothesis 2 tried to find out if technical, human, and organizational factors or errors have a correspondence to the technical (hypothesis 2.1), human factors (hypothesis 2.2), and institutional eras (hypothesis 2.3).The results show that most of the attributions in the technical period are technical factors, which would comply with hypothesis 2.1.However, in the era of human factors, hypothesis 2.2 is not met since the most numerous attribution errors are organizational ones.The majority of attributions are also fulfilled according to hypothesis 2.3 since, in both eras (institutional and total system), organizational factors are predominant (Figure 13).
With regard to the evolution of factors or errors from 1949 to nowadays, hypothesis 3 is fulfilled in that it predicts a decrease in technical errors and an increase in organizational errors, both in absolute value and in percentage.However, it is not fulfilled as far as human factors are concerned since the percent of human factors does not grow but has a decreasing tendency (the absolute values of each period first increase and then decrease).
The results of hypotheses 2 and 3 on human factors (which factors predominate at the time of human factors and the trend of the same during the period 1949-2020) raise the need for a more detailed analysis, separating causes and recommendations, in a similar way to the study carried out of determining causes, contributing causes and recommendations.Those relating to causes and recommendations show in isolation that human factors have a predominant weight in the former but not in the latter.Human factors are increasing in the causes until the institutional era and then decreasing in the present stage.Human factors predominate in the causes (Figure 14), while organizational factors predominate in the recommendations (Figure 15).

Conclusions
Another identified moment of change is located in the 70s and has as protagonist the vast increase in the normative development promoted by the ICAO.The transition between the technical era and the human factors era turned out to be the peak of the development of regulated aviation publications.This moment is prior to the period identified as significant in the proposed theoretical model (early 90s).The evolution of standards (SARPs) and procedures (PANS) of the Annexes has its highest increase just after the technical era.The reason justifying these results could be the urgent need, during the technical stage, for an integration between the human and technology factors (man-machine).Although, for the establishment of definitive conclusions, it will be necessary to wait for the results of new research.
Regarding the study of causes and recommendations, it is relevant to highlight that it is necessary to study both report conclusions in isolation (on the one hand, causes and, on the other hand, recommendations).Treating both attributions together distorts the behavior of the results in terms of human factors.In general, human factors predominate in the causes of the reports analyzed.On the contrary, organizational factors predominate in the recommendations throughout the period studied.The conclusion that emerges is that accidents caused by human factors generate in the investigations the issuance of safety recommendations of the organizational type.On the other hand, the pattern of technical factors is an explicit decrease, both in causes and recommendations.
From the results drawn from the analysis conducted, it is concluded that there is a fine line between the definition of a human error or factor and an organizational error or factor.Fatigue, for example, is a human factor, causing numerous errors, but the responsibility for not appearing on the scene is an organizational one.Another important conclusion of the study, without doubt, is that all the catastrophes studied have been a relevant advance for the air transport industry, but what will happen when there are no high-impact accidents?Will it be possible to continue learning?Undoubtedly, the current cornerstone to prevent accidents in the future, which answers this ques-tion, is the study of incidents.In the first edition of the International Civil Aviation Organization's (ICAO, 2006) Operational Safety Manual and in Frank Bird's theory, it was believed that the factors or causes that contribute to major catastrophes can be present in incidents and, therefore, these can be detected before grave damage occurs.This statement reflected by ICAO constitutes "the Heinrich/ Bird safety pyramid" of the 70s (Arnau, 2021).After learning from vast accidents, today, the safety pyramid of the 70s by Heinrich and Bird makes sense and is now more helpful in understanding the future of operational safety.There is no denying that critical accidents have produced and continue to produce relevant changes in the industry.However, nowadays, the industry seeks these changes hand in hand with the area of eventual knowledge, located at the base of the pyramid and directly related to daily operations, information on events, hazards, and systemic deficiencies.
The top of the pyramid is almost explored and constitutes the level of genuine knowledge provided by accident investigation.But the lower base is an unexplored area and represents a great learning opportunity through the optimization of data capture mechanisms (Martínez, 2016).Currently, there is more travel in learning about incidents than in studying fatal accidents or catastrophes, mainly because they occur less and less frequently.In this way, the systems of mandatory notification of almost any event or Aviation Data Reporting Program (ADREP) provide a large amount of information, typical of big data.Incident reporting and big data analysis research seem to be the future, making learning about the incident increasingly valuable so that it never becomes a major catastrophe (ICAO, 2006).
Therefore, the clearest recommendation that arises from all the results obtained in this study is to promote voluntary incident reporting systems within a positive safety culture (fair culture) and not to stick exclusively to mandatory reporting events.The safety culture is fundamental for achieving the voluntariness of making available to the global system all operational safety events to be studied as big data and thus be able to make more accurate predictions and recommendations (recommendations on the operational safety of global interest or SRGC).

Figure 1 .
Figure 1.Operational safety evolution reference periods

■
Quantitative variables: (1) the number of ICAO regulatory publications; (2) the global commercial aviation mortality rate; (3) the global commercial aviation air accidents rate; and (4) the global commercial aviation high mortality air accidents rate (accidents with more than 49 victims).

Figure 10 .Figure 11 .
Figure 10.Method of classification of causes and recommendations in the different factors.Period 1949-2020

Figure 12 .Figure 13 .
Figure 12.Percentages of technical, human, and organizational factors in the "recommendations"

Figure 14 .
Figure 14.Type of predominant factor in "causes" of the reports by era and their evolution

Figure 15 .
Figure 15.Type of predominant factor in "recommendations" of the reports by era and their evolution

Table 2 .
Loss of power from the right engine from catching fire before the aircraft reached the optimal ascent speed with a single engine, caused it to lose altitude and crash into the sea.Loss of power of the right engine, caused by the failure of the fastening bolts of cylinder No. 10, causing a fire in flight that became uncontrollable.The captain's persistent action in attempting to restore an ascent, without using all available power, caused the critical loss of power from another engine.He went into loss.Commercial aviation worldwide accident victims by safety era X MC-4 Defective engine parts.X R-1 It was recommended, in the future, to inform passengers about the location and use of flotation equipment and emergency exits before flights over water.X R-2 Provide boats and life jackets in appropriate locations, ready to be used.X Figure 9. Method of classification of causes and recommendations in the different factors Table 1.International Civil Aviation Organization (ICAO) Publications (1949-2020) and Annexes (amendments and editions)

Table 3 .
Commercial aviation worldwide accidents by safety era

Table 4 .
Commercial aviation worldwide high mortality accidents by safety era

Table 5 .
Technical, human, and organizational factors by evolutionary eras