Analysis of United States Civil Aviation Accidents

Effects of Severity of Accidents

The National Transportation Safety Board (NTSB) carried out research that happened over the period from 2001 to 2010 relating to civil aviation accidents on the commercial air transport sector. The air carriers fly large, transport aircraft engaged in revenue operations involving the transportation of both passengers and cargo.
The operators generally conduct operations in controlled airspace and controlled airports that provide specific weather, navigational, operational equipment and maintenance support. This article provides a meta-analysis done on the original data involving the broad categories of civil aviation accidents and the kinds of operations, the types of aircraft, and the pilots involved in them.

Year 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
Major 5 1 2 4 2 2 0 4 2 1
Serious 1 1 3 0 3 2 2 1 3 0
Injury 19 14 24 15 11 7 14 8 15 13
Damage 20 25 25 11 24 22 12 15 10 14
Total 45 31 54 29 40 33 28 28 30 28
Mean per Year 11.3 7.8 13.5 7.3 10.0 8.3 7.0 7.0 7.5 7.0
Standard Deviation 13.3 11.9 12.7 6.8 10.1 9.5 7.0 6.1 6.1 7.5
Effect Size 0.3 0.3 0.3 0.3 0.2 0.3 0.3 0.2 0.2 0.2
Effect Interpretation Small Small Small Small Small Small Small Small Small Small

Table 1: Categorisation of Severity of Accidents from 2001 – 2010, Mean and Standard Deviation

Table 1 illustrates the total civil aviation accidents for commercial air transport sector that occurred from 2001 to 2010. From Cohen's, there was a small delta of 0.2 to 0.3 which has a small effect. From Table 1, the severity of accidents has declined over the decade and the severity is either injury or damage. This shows that through the discipline of flight safety, the frequency and severity of aviation occurrences have declined significantly. Accident prevention is everyone’s responsibility which includes international organizations, major aircraft and power-plant manufacturers, state regulatory authorities for civil aviation, owners and operators, maintenance organizations, industry and professional associations, aviation education and training institutions. Table 1 shows a normal distribution as the data is perfectly normal.

Contributing Factors No. of Aircrafts Percentage % Means Difference
Turbulence Encounter 8 25.8 No significance
Ground Collisions 5 16.1 No significance
Ground Handling 4 12.9 No significance
Birdstrike 3 9.7 No significance
Abrupt Manoeuvre 2 6.5 No significance
Cabin Safety 2 6.5 No significance
System Failure 2 6.5 No significance
Other Collision 2 6.5 No significance
Unknown 2 6.5 No significance
Thunderstorm/Windshear 1 3.2 No significance
Total 31 100
Mean 3.1
Mode 8
Standard Deviation 2.1

Table 2: Contributing Factors, No. of Aircraft, Percentage, Means Difference, Mean, Mode and Standard Deviation in 2010

Table 2 displays the contributing factors and number of aircrafts accidents for commercial air transport sector in 2010. The most predominant cause of accident was turbulence encounter. Turbulence encounters accounted for more than a quarter of the accident events. The next cause of accident was ground collision when one of the aircraft involved is taxiing to or from a runway. The mode is the most frequent score in the data set. However, on a histogram, it represents the highest bar which is turbulence encounter. Turbulence encounter may occur without warning thus it is difficult to minimize the accident. For the rest of the contributing factors, it can be reduced. This indicates that if crew resource management and accident prevention are put in place, it is possible to achieve zero accident. Table 2 shows that the data are normally distributed as the data distribution is continuous and symmetrical.
From Table 2, the comparison of the contributing factors is not significant difference when p value <0.05.

Study Scope

The purpose of this study is to determine number of civil aviation accidents on the commercial air transport sector annually and determine the factors which lead to these accidents.


Research Approach

Research on the severity of civil aviation accidents in the commercial air transport sector.


A list of total civil aviation accidents for commercial air transport sector that occurred from over the decade between 2001 and 2010. The number of accidents happened in 2010 are categorised to the individual factors that contributed to the accidents.

Data Analysis

Descriptive statistics was used for data analysis. The meta-analysis provides further descriptive statistics such as central tendency, dispersion and effect size.

1. National Transportation Safety Board (2010). Review of U.S. Civil Aviation Accident.
2. Wikipedia (2013). Effect Size.
+++ Footnotes +++


Description of contributing factors

Contributing Factors Description
Turbulence Encounter Motion of air caused by changes in air currents
Ground Collisions Ground operations when one of the aircraft involved is taxiing to or from a runway
Ground Handling Ground handling, jet blast, near collision on ground with aircraft or vehicle, propeller strike, or runway incursion
Birdstrike Bird or animal strike
Abrupt Manoeuvre Inappropriate execution of flight planning decisions. Mishandling of the aircraft including unnecessary manoeuvres and inappropriate emergency responses
Cabin Safety Crew illness or incapacitation
System Failure Aircraft systems including fuel, instrument air power, and pressurization
Other Collision Other accidents
Unknown Intentional damage and inaccurate metrological information
Thunderstorm/Windshear Weather

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