Prevalence of Fatigue in a Group of Airline Pilots


Reis, Mestre and Canhao conducted a research about fatigue in modern aviation specifically in commercial aviation industry in 2012[1]. The study provides the first prevalence value for clinically significant fatigue in a group of Portuguese airline pilots with two different type of flight operations: medium/ short haul and long haul. Reis et. al hypothesized that different type of flight operations may create different levels of fatigue. This article provides a meta-analysis based on the original results.


Table 1: Fatigue Severity Scale (FSS) Result

Physical/Total fatigue Mental
Medium/ Short haul 93% 96.5%
Long Haul 84.3% 92.1%
Total* 89.3% 94.1%
*Total include 15 participants who fly both Medium/Short haul and Long haul

For the total sample of Portuguese airline pilots, a percentage value of physical/total fatigue of 89.3% was obtained (this percentage include 15 pilots who flew both types of flight). The values from the 15 pilots were only included when analyzing the total sample and not considered as a separate group. For medium/short-haul flight, a percentage value of 93% was obtained and 84.3 % for those pilots who flew long-haul. Regarding mental fatigue, a percentage value of 94.1% was obtained for the total sample of Portuguese airline pilots, 96.5% for medium/short haul pilots and 92.1% for long-haul pilots.

It can be seen from table 1 that different type of flight operations create different levels of fatigue. It also appears that medium/short haul pilots presented the highest level of both physical and mental fatigue with percentage values of 93% and 96.5 % respectively.

Table 2: Perception of Fatigue among Portuguese Airline Pilots

Questions Never (1) Once (2) Few Times (3) Frequently (4) Mean
“Do you feel so tired that you think you should not be in controls?” 60 (13.2%) 87 (19.1%) 234 (51.3%) 75 (16.4%) 2.71
“Have you ever reported yourself unfit for flight as a result of accumulated fatigue?” 372 (81.6%) 50 (11%) 28 (6.1%) 6 (1.3%) 1.27

Concerning fatigue perception, table 2 shows that the majority of participants felt so tired that they think they should not be in control at least a few times. However, it can be seen that the majority of participants never reported themselves unfit for flight. This is a safety issue as fatigued pilot will not be able to safely operate an aircraft or perform safety related duties [3]. This was not highlighted in the article.

Table 3: Report of Fatigue among Portuguese Airline Pilots

Questions Mean SD
“How many Human Factors Confidential Reports have you made in the last six months?” Min. 0 Max. 14 0.38 1.15
371 (81.4%) 1 (0.2%)
“Has it ever happened that you have made mistakes in the cockpit as a direct consequence of fatigue?” Yes No - -
417 (91.4%) 39 (8.6%)

Table 3 Highlights the majority of participants (371; 81,4%) had not made any 'Human Factors Confidential Reports' in the last six months, with a mean of 0.38 and SD of 1.15. However, 417 (91.4%) of the participants reported that the mistakes they have made in the cockpit was a direct consequence of fatigue. Another safety concern is that airlines may be unaware of pilot fatigue; due to the fact that pilots are not reporting fatigue or its varying effects based on flight operation.


Research approach

Exploratory research into the fatigue levels of Portuguese airline pilots who fly medium/short-haul and long-haul.


From the population of 1500 commercial airline pilots working in Portuguese airlines, 456 sample were obtained with the criteria: airline pilots on active duty (Commanders and First Officers), age between 20 and 65 yr old and having flown during the last 6 month.
Sub-sample : medium/short haul pilots and long haul pilots.


A survey was conducted by requesting Portuguese airline pilots to complete questionnaires from 1 April to 15 May 2012. The questionnaire includes 9-item Fatigue Severity Scale (FSS) self-report questionnaires to measure fatigue and additional questions concerning perception of fatigue by pilots. To validate the survey, a pretest was used. The pretest was answered by a sample of 104 pilots from mid-January to mid-February 2012. FSS score ranges from 1 to 7, where 1 indicates strong disagreement and 7 indicates strong agreement. The cutoff value for clinically significant fatigue in the FSS scale is 4.


The Fatigue Severity Scale (FSS) presented two dimensions: mental and physical fatigue[1]. Mental fatigue refers to the feeling that people may experience after or during prolonged periods of cognitive activity and characterized by lack of motivation and of alertness[2] . It involves fatigue, exhaustion, decreased level of commitment to the task and may lead to a strong will to stop performing[4]. While physical fatigue refers to reduced physical performance after or during prolonged periods of physical activity and characterized by lack of energy or strength on performing task[2].

Data Analysis

The original articles highlighted several areas such as the percentage value of fatigue among pilots and the perception of fatigue among pilots. This meta - analysis, however, provides further analysis and draw further conclusion based on the result given in the article.

1. Reis, C., Mestre, C., & Canhao, H. (2013). Prevalence of Fatigue in a Group of Airline Pilots. Aviation, space, and environmental medicine, 84(8), 828-833.
2. Sharpe, M. C., Archard, L. C., Banatvala, J. E., Borysiewicz, L. K., Clare, A. W., David, A., … & Lane, R. J. (1991). A report—chronic fatigue syndrome: guidelines for research. Journal of the Royal Society of Medicine, 84(2), 118.
3. International Civil Aviation Organization. (2012). Manual of civil aviation medicine (3rd Ed.). Doc. 8984-AN/895, Part II, Chapter 1; II-1-1 – II-1-18 . Montreal, Quebec: Canada
4. Boksem, M. A., & Tops, M. (2008). Mental fatigue: costs and benefits. Brain Research Reviews, 59(1), 125-139.

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