A Simple Way For Pilots To Combat Aviation Fatigue

Unsolved Issues: Part V, Amber Berlin

To read Part 1, click here, Part 2, click here, Part 3, click here, and Part 4, click here.

Are you tired? Maybe you need a nap.

Naps decrease the homeostatic drive for sleep by reducing the number of hours continuously awake, which results in a greater ability to focus. It’s like a reboot for your brain, shutting down the conscious processes of thought in favor of cellular recovery and the cleanup of waste chemicals. Studies indicate pilots afforded sleep during in-flight crew rest performed better on cognitive tests than those pilots who were only given a rest period where sleep was not permitted. But to most effectively combat aviation fatigue, when is the best time of day to take a nap? And how long should you nap to get the most benefit?

The best time of day to nap is during a Window of Circadian Low. The Window of Circadian Low refers to a specific time of day within the 24-hour circadian cycle in which subjects are primed for sleep. During times of circadian peak, the body’s physiological processes are programmed for an increased level of wakefulness. Conversely, during dips in the circadian cycle the body is gearing down for sleep.

Staying awake during a Window of Circadian Low can cause an increased level of fatigue because the pilot is working against the physiological processes which are preparing for sleep. Quite literally, you are fighting against your body to stay awake. Within the circadian cycle, researchers have identified two Windows of Circadian Low: at approximately 3am-5am and 3pm-5pm (Rosekind, Co, Gregory, and Miller, 2000). Many of us struggle through the afternoon hours yawning and drinking coffee, so if you get the opportunity, take advantage of the 3pm circadian siesta. Studies have also shown operations during a Window of Circadian Low can result in reductions in performance and alertness and increases in micro sleeps and errors (Rosekind, Gander, Connell, & Co, 2001; Caldwell et al., 2006).

The normal sleep cycle runs approximately 90 minutes and is comprised of sleep stages 1-4 and rapid-eye-movement (REM). Getting through an entire sleep cycle is a good idea, however, there are hazards to sleeping too long on your nap. Sleep inertia is defined by the Federal Aviation Administration as “… a period of impaired performance and reduced vigilance following awakening from the regular sleep episode or nap. This impairment may be severe, last from minutes to hours, and be accompanied by micro-sleep episodes” (FAA, 2010). Otherwise known as grogginess, sleep inertia can make waking up from your nap an undesirable experience as you try to get your bearings.

If you can’t get the full sleep cycle in, aim for less than 45 minutes, which reduces the occurrence of sleep inertia. By avoiding the deeper stages of sleep, you can also avoid the grogginess that comes with waking up in them. But remember, the best recovery happens in those final sleep stages and it’s important to spend as much time there as possible.

Flying unconscious….have you done it lately? Find out how you can combat aviation fatigue and this zombie-like behavior in the next Unsolved Issues: Part VI – Nocturnal Window of Unconscious Flight.

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Caldwell, J., Mallis, M., Colletti, L., Oyung, R., Brandt, S., Arsintescu L., . . . & Chapman, P. (2006). The Effects of Ultra-Long-Range Flights on the Alertness and Performance of Aviators. NASA/TM-2006-213484.

Federal Aviation Administration (2010). Advisory Circular. Basics of Aviation Fatigue. AC No. 120-100.

Rosekind, M., Co, E., Gregory, K., and Miller, D. (2000). Crew Factors in Flight Operations XIII: A Survey of Fatigue Factors in Corporate/Executive Aviation Operations. NASA/TM–2000-209610.

Rosekind, M., Gander, P., Connell, L. and Co, E. (2001). Crew Factors in Flight Operations X: Alertness Management in Flight Operations Education Module. NASA/TM-2001-211385/DOT/FAA/AR-01-01.

Featured Image: Kent Wien

Looking at Stress and Fatigue in Aviation

Unsolved Issues: Part IV, Amber Berlin

To read Part 1, click here, Part 2, click here and Part 3, click here.

Think you wouldn’t drink and fly a plane? You might be doing something similar without even realizing it. This article reveals the exact hour limit when your long day becomes intoxicating, and why you wouldn’t realize when it happens. Understanding your limits, and how they’re affected by stress and fatigue in aviation is knowledge that will make you a better pilot, and may even save your life.

Scientists currently believe that stress and fatigue in aviation are developed from a variety of sources, and no one is immune from them. Although the effects on the body are different, excessive exposure to mental stimulation produces the same measurable results as extensive manual labor and leads to a decrease in the ability to carry out tasks. (FAA Publication, Medical Facts for Pilots, 2002). Any person operating in a fatigued condition, regardless of the cause of fatigue, will exhibit the same problems.

Historically, research indicates obtaining adequate sleep is the best way to prevent or resolve stress and fatigue in aviation. However, because of the complex nature of the body’s response to a variety of factors other than sleep deprivation, adequate sleep is not to be considered a complete solution in fatigue management. Because of the dynamic environments in which we operate, our body’s experience a myriad of situations and events which lead to the effects of fatigue. Sleep deprivation directly contributes to fatigue because the body does the majority of its recovery during sleep.

Sleep Deprivation

Sleep deprivation refers to no sleep or a reduction in the usual total sleep time. Various amounts of sleep deprivation have shown to reduce cognitive function and can negatively impact performance levels. Sleep deprivation affects the performance of sustained attention tasks and manifested itself in a higher number of omission errors (Fafrowicz et al., 2010). These omission errors, defined as “lapsing or failing to respond in a timely fashion to a presented stimulus”, are related to micro sleeps and increase under high fatigue conditions (p.940).

Durmer and Dinges (2005) conducted several partial sleep deprivation studies, which indicate a suboptimal sleep dose has measurable effects on concentration and the performance of cognitive tasks. Reports have shown that the average sleep obtained by a pilot is approximately 6 hours per night. Over a two-week span, the body’s response to sleeping only 6 hours per night is similar in cognitive ability to operating under an entire night of sleep loss. Think about this for a moment…let it sink in…the average pilot is operating on a day-to-day basis, flying their aircraft with the same cognitive ability as if they’ve just been awake all night.

For those individuals receiving only 4 hours of sleep during the same span, the cognitive effects are comparable to an entire weekend of sleep loss (Durmer and Dinges, 2005). Hopefully, you are all getting more than 4 hours a night. While no cognitive deficits occurred for 8 hours of sleep per night, 1 hour of sleep loss per night causes reduced waking alertness, and 2 hours of sleep loss can “significantly affect both alertness and performance” (Rosekind, Co, Gregory, and Miller, 2000, p,4). These studies have shown there is a consistent decline in cognitive ability due to sleep loss and denote the importance of attaining the recommended 8 hours of sleep per night.

It is also known that subjective reports of fatigue are typically underestimated, as individuals “are often sleepier than they report” (Overton and Frazer, 2013, p.219). Studies using physiological measures of sleepiness have shown that people can, “report a high level of alertness during the day and yet still exhibit significant physiological sleepiness” (Neri, Dinges, and Rosekind, 1997, p.11). This alludes to the role of environmental stimulation in the individual perception of stress and fatigue in aviation and identifies a cognitive disassociation between how the subject feels and their actual physiological state. This disassociation inhibits the pilot from realizing when they are fatigued, thereby making it impossible to accurately report their fatigue level. If you ask the pilot, they will feel rested enough to fly, even if they are not. Without as much environmental stimulation, such as in the early hours of the morning, their actual level of physiological sleepiness may make it impossible to stay awake.

Kuo et al. (1998) found that “during chronic partial sleep deprivation, subjective sleepiness increased during the first week, but decreased during the second week, suggesting that subjects believed they were adapting to the effects of sleep loss, whereas performance measures indicated that they were not: (Kloss, Szuba, and Dinges, 2012, p.1900). Because of this illusion of adaptation to the effects of chronic partial sleep deprivation, pilots may believe they are fit for duty when in fact they are experiencing a dangerous level of fatigue. While most pilots are not subject to periods of acute total sleep deprivation, chronic partial sleep deprivation is a highly common occurrence in the aviation operational environment. Because of the effects of fatigue on perception, when “attempting to judge how sleepy an individual is, the worst person to ask is that individual” (Neri, Dinges, and Rosekind, 1997, p.11).

An American Airline flight departing LAX

Photo by: Job Garcia

Cumulative Sleep Loss

Another factor which must be considered is cumulative sleep loss, or sleep debt. Sleep debt is the accumulation of missed sleep over several days or weeks, which an individual has not had the opportunity to make up. Any sleep of less than 8 hours per night may result in a sleep debt. If you miss three hours of sleep on Wednesday, and one hour of sleep on Thursday, by Friday you are operating under 4 hours of missed sleep. According to one study, it takes more than the recommended 8 hours of sleep to make up a sleep debt, as sleeping 8 hours merely fulfills the daily requirement for sleep, thus “two nights of recovery sleep are typically needed to resume baseline levels of sleep structure and waking performance and alertness” (The Royal Aeronautical Society, n.d.).

Cumulative sleep loss can be any combination of total or partial sleep loss, and cognitive effects have been shown in as little as 1 hour of missed sleep per night. Studies have shown that “4 or more days of partial sleep restriction involving less than 7 hours sleep per night resulted in cumulative adverse effects on neurobehavioral functions” (Durmer and Dinges, 2005, p.123). Along with the increase in sleep debt, there is also an increase in attention lapses and daytime sleep propensity, and a decrease in cognitive speed and accuracy on working memory tasks (Van Dongen, Maislin, Mullington, & Dinges, 2003; Drake et al., 2001; Dinges et al., 1997; Belenky et al., 2003).

Hours of Continuous Wakefulness

Hours of Continuous Wakefulness refers to the number of hours since the last sleep episode. Durmer and Dinges (2005) suggested that there is a critical period of stable wake time within each circadian cycle, after which neurocognitive deficits occur. They have statistically estimated the optimal sleep time to be 8.16 hours, with the corresponding 15.84 hours of wakefulness completing the 24-hour circadian cycle (Durmer and Dinges, 2005).

According to current research, there is a drive for sleep which increases progressively with the duration of time the individual spends awake. In a study comparing the cognitive effects of this homeostatic sleep drive and the cognitive effects of alcohol, The Royal Aeronautical Society found, “after 17 hours of continuous wakefulness, cognitive psychomotor performance decreased to a level equivalent to a blood alcohol concentration of 0.05%”, and “after 24 hours of continuous wakefulness performance was approximately equal to a blood alcohol concentration of 0.10%” (n.d.). Additionally, NTSB investigations have found that flight crews on long duty days (a shift of more than 13 hours) exhibit a disproportionate amount of accidents when compared to those on short duty days (a shift of less than 13 hours) (Federal Aviation Administration, 2010).

The legal limit of alcohol intoxication to operate a vehicle in most States is 0.08%. To put it into perspective, if you have been awake for 17 hours, your brain responds as if you were over halfway drunk by vehicle standards, and over the limit to fly an aircraft. The federal blood alcohol limit for pilots is 0.04%. Should you be flying 17 hours after waking up? Absolutely not. This poses a problem for pilots working evening shifts, as they probably woke up early in the day, and were awake all day, and then started their shift, putting them in a situation where they are operating under the influence of fatigue. The FAA has taken a hard line against alcohol, adhering to the strict limit of 0.04%. Out of the thousands of pilots tested each year, only a few of them fail the breathalyzer, and alcohol-related crashes are rare. Since pilots cannot come to work drunk, it makes sense to limit their operational usefulness if they are known to have been awake for a duration in which intoxicating effects are present, regardless of the cause. Schedulers should also be aware of this limitation caused by stress and fatigue in aviation, and not assign pilots more flights than safety permits, based on the duration of time they’ve been awake.

Will a nap at noon be as good as a nap at 3pm? Find out as we continue our quest for cognitive excellence in Unsolved Issues: Part V – A Simple Way For Pilots To Address Aviation Fatigue.

Get Started With Your Flight Training Today

You can get started today by filling out our online application. If you would like more information, you can call us at (844) 435-9338, or click here to start a live chat with us.


Belenky, G., Wesesten, N.J., Thorne, D.R., Thomas, M.L., Sing, H., Redmond, D.P., …Balkin, T.J. (2003). Patterns of performance degradation and restoration during sleep restriction and subsequent recovery: a sleep dose-response study. Journal of Sleep Research 12, 1-12.

Dinges, D.F., Pack F., Williams, K., Gillen, K., Powell, J., Ott, G., …Pack, A. (1997). Cumulative sleepiness, mood disturbances, and psychomotor vigilance performance decrements during a week of sleep restricted to 4-5 hours per night. Sleep 1997; Apr 20(4):267-277

Drake, C., Roehrs T., Burduvali, E., Bonahoom. A., Rosekind, M., Roth, T. (2001) Effects of rapid versus slow accumulation of eight hours of sleep loss. Psychophysiology 2001;38: 979-987.

Durmer, J., Dinges, D. (2005). Neurocognitive Consequences of Sleep Deprivation. Indiana University School of Medicine.

FAA Publication. (2002). Medical Facts for Pilots. Federal Aviation Administration

Fafrowicz, M., Oginska, H., Mojsa-Kaja, J., Marek, T., Golonka, K., and Tucholska, K. (2010) Chronic Sleep Deficit and Performance of a Sustained Attention Task- an Electrooculography Study. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/20636207

Federal Aviation Administration. (2010). Basics of Aviation Fatigue. AC No 120-100. Retrieved from http://www.faa.gov/documentLibrary/media/Advisory_Circular/AC%20120-100.pdf

Kloss, J., Szuba, M., and David, D. (2012). Sleep Loss and Sleepiness: Physiological and Neurobehavioral Effects. Neuropsychopharmacology: The Fifth Generation of Progress. C130: 1895-1906.

Neri, D. F., Dinges, D. F., Rosekind, M. R. (1997). Sustained Carrier Operations: Sleep Loss, Performance, and Fatigue Countermeasures. Fatigue Countermeasures Program. NASA Ames Research Center.

Overton, J., Frazier, E. (2013). Safety and Quality in Medical Transport Systems: Creating an Effective Culture. Ashgate Publishing Ltd: England.

Rosekind, M., Co, E., Gregory, K., and Miller, D. (2000). Crew Factors in Flight Operations XIII: A Survey of Fatigue Factors in Corporate/Executive Aviation Operations. NASA/TM–2000-209610.

The Royal Aeronautical Society Publication.(n.d.). Fatigue and Duty time Limitations- An International Review. The Royal Aeronautical Society.

Van Dongen, H. P. A., Maislin, G., Mullington, J. M., and Dinges, D. F. (2003). The cumulative cost of additional wakefulness; Dose-response effects on neurobehavioral functions and sleep physiology from chronic sleep restriction and total sleep deprivation. Sleep 26(2), 117-26.

Featured Image: Kent Wien

Working to Address The Problem of Fatigue in Pilots

Unsolved Issues: Part 3, Amber Berlin

To read Part 1, click here, and to read Part 2, click here.

In order to achieve a viable solution for fatigue in pilots, we must consider the current beliefs, opinions, and assumptions in the science of fatigue and fatigue management. There is a general consensus in the scientific community about what causes fatigue, and much research has been accomplished in studying the body’s response to operation in the realm of fatigue. Several factors have been proven to contribute to an individual’s level of fatigue, including diet, level of physical activity, circadian disruption, the presence sleeping disorders and exposure to sustained stress. Since there are several factors which contribute to fatigue in pilots, each of these factors must be addressed and an appropriate solution achieved.

The situations and pressures that cause stress are known as stressors. We usually think of stressors as being negative, such as a taxing work schedule or poor relationship. However, anything that puts a high demand on you or forces you to adjust can be stressful. This includes positive events such as getting married, buying a house, or simply receiving a promotion. Prolonged stress has certain degrading effects on the body, which includes cognitive symptoms, such as the inability to concentrate; emotional symptoms, such as feeling overwhelmed; physical symptoms such as nausea and dizziness; and behavioral symptoms such as the inability to sleep.

Each individual’s tolerance for stress is unique. Some people can handle more stress than others due to their individual experiences and psychological makeup. According to an article by Dr. John Anne titled Stress Reduction – Which Techniques Can Be Used to Reduce Stress, stress creates a physical condition that increases the occurrence of various health problems:

“Chronic stress may lead to unpleasant conditions even for the strongest individuals. Prolonged stress can cause a permanent biochemical imbalance in the health system. This eventually leads to a weakened immune system and increased vulnerability for serious health conditions, which may be proven fatal in due course of time. Stress is known to develop various health complications such as asthma, cardiac complication, high blood pressure, allergy, fatigue, depression, insomnia, anxiety, irregular bladder, headaches, body pain and many more. (2007).”

If you do not manage long-term stress effectively, it can lead to long-term fatigue, failure, or one of the many forms of physical or mental ill health.

It is known that pilots experience high levels of stress due to the sustained attention and decision-making capability required to fly an aircraft. Gregory, et.al have shown that during the descent phase of flight, the pilot controlling the aircraft experiences an increased heart rate, signifying an increased level of stress. (1994). When under the effects of stress, the body responds by emitting cortisol from the adrenal glands located on the upper side of the kidneys. Cortisol is produced to assist the body’s natural response to stress, the need to fight or flee the situation. In an aviation environment, there is no one to fight, and nowhere to flee, so this cortisol is not used appropriately. With no outlet, the cortisol remains in the system in high levels for an extended period of time, doing damage to the cells of the brain and body, and resulting in sustained levels of anxiety and reduced cognitive ability.

Photo by: Michael Coghlan

Photo by: Michael Coghlan

One reliable way to reduce cortisol levels in the body is massage. According to a study conducted by the University of Miami School of Medicine, “cortisol levels decrease dramatically post massage, and have been reported decreasing by as much as 37% over recorded pre-massage levels.” (2005). Massage also increases the level of dopamine, a brain chemical which is responsible for keeping the brain alert and awake, and serotonin, which works against cortisol, producing a calm and relaxed state. (University of Miami School of Medicine, 2005).

Studies have shown that massage will decrease the effects of stress and fatigue on the body by speeding the elimination of chemical waste produced by the body, in both animals and humans. This information has been around for quite some time, as J.H. Kellogg, M.D. wrote in The Art of Massage about the ability to remove the effects of fatigue by administering massage:

“In cases of exhaustion from excessive mental, nervous, or muscular work, general massage secures the most marked and satisfactory results, relieving the sense of fatigue in a most wonderful manner, and in cases of muscular exhaustion, restoring muscular power in a remarkably short space of time. Ranke, Helmholtz, Du Bois-Raymond, and more recently, Abelous, have conclusively shown that special toxic substances are produced as the result of muscle work, and that the phenomena of fatigue are due to the influence of these substances upon the nervous and muscular systems. Zabloudowski has shown that frogs completely exhausted by faradization of the muscles, although not restored by fifteen minutes’ rest, were revived at once by massage, and were even able to do twice as much work as before. In another experiment, a man lifted with his little finger, one kilo (2 1-5 lbs.) 840 times, lifting the weight once a second. The muscles of his finger were then completely exhausted. After five minutes’ massage he was able to lift the same weight 1100 times, and his muscles were even then not greatly fatigued. Mental fatigue is also relieved by massage, through its effect upon the circulation and the eliminative organs. The toxic substances produced by mental activity, are more rapidly oxidized and removed from the body, while the hastened blood current more thoroughly repairs and cleanses the wearied nerve tissues. The entire nervous stem, through the improved nutrition induced by massage, experiences general reconstructive effects. (1895).”

A certified massage therapist, Vicki Platt, highlighted recent findings on the effects of massage in the workplace, including a five-week study at Bowling Green State University, proving massage has the ability to increase mental alertness:

“The individuals who participated in the study were massaged twice a week and completed a math test in half the time, with half the errors as the control group. (2007).”

The investigations listed herein have shown that massage is one of the most effective ways of influencing the human body’s ability to eliminate toxic substances, and thereby recover from both mental and physical fatigue. Massage has the ability to speed the recovery from fatigue at several times the rate of rest alone, and revive the muscles to potentially do more work than they previously could. As massage speeds the removal of the chemicals that build up in the brain, the way is cleared for the continued chemical processes of decision making and sustained attention required for flight. As the waste products are removed, mental clarity is restored and faster response times become possible. Massage results in faster recovery from fatigue in pilots and resets the body’s ability to handle the next dose of stress and fatigue aviation schedules deliver. This information is not new, but it has not been applied to the aviation industry as a legitimate finding on fatigue, and as of now there are no programs available that incorporate these principles.

A massage program, when applied to the aviation industry, has the potential to reduce fatigue in pilots and thereby increase safety, and should be incorporated for those positions which normally experience high levels of stress. While it’s not practical or cost effective to provide each pilot with a personal post-flight massage, obtaining a massage chair for regular home use, and a couple of massage chairs in each pilot’s lounge is highly recommended to relieve the effects of fatigue in pilots, promote better sleep, and keep cortisol levels to a minimum. A program to finance massage chairs during flight training would put the solution for the problem of fatigue in pilots where it’s needed the most, and has the potential to reduce training times due to the increased ability to focus and process information. An airline safety program element to provide massage chairs for post-flight use in pilot lounges would increase safety and reduce overall healthcare costs for the airline. As we hold consistently high standards for our pilots, we can also give them the tools to be successful in delivering consistently excellent results. Massage is the missing link in the fight against fatigue in pilots. Although it seems like a luxury item to many, science has proven it to be a necessity for the sustained 24-hour operations and attentional requirements of our top performers, the pilots.

Think you wouldn’t drink and fly a plane? You might be doing something similar without even knowing it. As our journey to cognitive excellence continues, we’ll see the scientific comparison between being awake and being drunk in Unsolved Issues: Part IV, Stress and Fatigue in Aviation: Looking at Continuous Wakefulness and Sleep

Get Started With Your Flight Training Today

You can get started today by filling out our online application. If you would like more information, you can call us at (844) 435-9338, or click here to start a live chat with us.


Anne, John. (2007). Stress Reduction – Which Techniques can be used to Reduce Stress.

Gregory, K. B; Miller, D. L; Lebacqz, J. V.; Mcnally, K. L; Weldon, K. J; Rosekind, M. R; Co, E. L;Smith, R. M; Gander, P. H. (1994). Fatigue in Operational Settings: Examples from the Aviation Environment. Human Factors 36:2 p. 327-338.

Kellogg, J.H. (1895). The Art of Massage. Retrieved from here and here.

Platt, Vicki. (2007) Massage, The Healing Power of Touch can Help Relieve Pain.

University of Miami School of Medicine. (2005). International Journal of Neuroscience. Cortisol decreases and serotonin and dopamine increase following massage therapy. Int J Neurosci. 2005 Oct;115(10):1397-413.

Featured Image: Matthew Juzenas

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