Effects of fatigue on safety

Fatigue can be a symptom of a medical problem, but more commonly it is a normal physiological reaction to exertion, lack of sleep, boredom, changes to sleep-wake schedules (including jet lag), or stress.

The International Civil Aviation Organization (ICAO) that codifies standards and regulations for international air-navigation defines fatigue as: "A physiological state of reduced mental or physical performance capability resulting from sleep loss or extended wakefulness, circadian phase, or workload (mental and/or physical activity) that can impair a crew member's alertness and ability to safely operate an aircraft or perform safety related duties.

[12] In 1999, the National Aeronautics and Space Administration, NASA, testified before the U.S. House of Representatives that pilot fatigue impacts aviation safety with "unknown magnitude".

The report cited evidence of fatigue issues in areas including aviation operations, laboratory studies, high-fidelity simulations, and surveys.

[13] In 2009, Aerospace Medical Association listed long duty work hours, insufficient sleep, and circadian disruptions as few of the largest contributing factors to pilot fatigue.

[19] Safety experts estimate that pilot fatigue contributes to 15-20% of fatal aviation accidents caused by human error.

The same view of fatigue as a major risk factor is shared by leading scientists in the area, as documented in several consensus statements.

According to numerous studies, the risk of fatigue is greatest between the hours of midnight and six in the morning, and increases with the total length of the driver's trip.

[27] Quality of their sleep may be affected by a variety of factors:[26] quality of the food on board, the vibrations due to the engine and waves, the noise of repair or works or engine, only naps (not sleeping eight hours in a single run but two or three naps a day) because of the watch system and secondary jobs.

The ILO have conventions for trying to restrict the maximum working hours on board and to determine the minimum rest period of seafarers.