Flying Tired: Recovery From Sleep Loss Is Not So Simple

Many of us as youngsters yearned to become pilots. We envisioned the “glamorous” jet-setting lifestyle with plenty of comely companionship on trips to exotic locations like Rio, Tahiti and Paris, feasting on the local cuisine and strolling along wide beaches and narrow cobblestone streets. Little did we know that the occupation would involve long duty days, early starts, multiple time zone changes, uncomfortable hours confined in a tight cockpit while breathing desert-dry air and forcing ourselves not to nod off.

John A. Caldwell, Ph.D., co-author of Fatigue in Aviation, is an internationally recognized scientist in the area of sleep deprivation and fatigue countermeasures. He asserts that “fatigue-related performance problems in aviation have been consistently underestimated and underappreciated” despite decades of research on pilots showing that insufficient sleep significantly degrades cognition, psychological mood “and fundamental piloting skills.”


Image Source: istockphoto

None of us are immune to the problems of fatigue. If you have found yourself or crewmates overlooking or misplacing sequential steps, becoming preoccupied with single tasks, having a greatly reduced audiovisual scan and being less aware of poor performance, then welcome to the brotherhood of the flying weary. Other notable warning signs of fatigue include being less likely to perform low-demand tasks, becoming more distracted and more irritable, and finally succumbing to a “don’t care” attitude.

The only way to recover from fatigue is to get adequate rest. Unfortunately, that’s often not an option. Dr. Curtis Graeber, who served as the human factors specialist for the Presidential Commission on the Space Shuttle Challenger Accident, joined NASA Ames Research Center in 1981 as the principal investigator for a congressionally mandated study of fatigue and circadian rhythm factors in flight crews. The NASA research team found that the sleep deficit for a tour often begins before showing up for the first trip, especially if the report time involves an early wake-up. Under such frequent circumstances, the average pilot reports for duty on day No. 1 with a sleep deficit. Strike one.

If you feel that your sleep on the road is less restful that your sleep at home, you aren’t alone. NASA studies found that the average pilot sleeps an hour less per night during layovers than at home due to the significant increase in awakenings while in hotel rooms. Such sleep disruption is known to result in daytime sleepiness. That’s strike No. 2.

Let’s say you flew the “back side of the clock” and dragged your weary bones into the hotel room at 5 a.m. How many times has the chambermaid knocked on your door a few hours later loudly proclaiming, “Housekeeping,” despite the “Do Not Disturb” sign you hung on the exterior doorknob? And is it too much to ask hotels to put a “quiet close” device on guest room doors so that guests can’t slam them shut?

The quality of the sleep environment is an important contributor to rest and recovery, yet we pilots have no control over it and simply have to endure less-than-restful nights when on the road. That’s strike No. 3. But wait, there’s more to the fatigue problem.

Have you felt yourself getting even more tired during the progression of a tour? This, too, is commonplace since the lack of adequate rest accumulates. This “sleep debt” or “sleep deficit” is real and a real problem. Consider this: You have the dreaded 5:00 a.m. show on day No. 1 of a trip beginning at your home base at Van Nuys Airport (KVNY) in California for a nonstop to Chicago Midway Airport (KMDW), where you pick up additional passengers and continue to New Jersey’s Teterboro Airport (KTEB). Depending on your driving time to the FBO at Van Nuys, it’s quite possible you had to wake up at 3 or 3:30 a.m. Once at the New Jersey hotel, you might try to sleep around 7 p.m., but there’s the call home, shirt pressing, emails and such, and it’s more likely you’ll be lights out at 11 p.m., your normal sleep time. You’ve made it through the day with, maybe, 4 hr. of sleep. Any normal pilot would have felt groggy all day long.

The next morning, you’re bound for Toronto’s Pearson International Airport (CYYZ) with a departure time of 7 a.m. With the paperwork for the international trip you plan to be at the FBO no later than 5:30 a.m. local, which translates to a 4 a.m. wakeup. Will you drop immediately into deep restful sleep? Not likely.

According to Graeber, when sleep is attempted at a time abnormal to a person’s circadian rhythm, that person will have considerably more difficulty getting to sleep and, once successful, will usually awaken within a relatively short time. This is one of the key underlying problems for pilots that creates what is essentially a career-long battle with fatigue. Simply stated, humans get their normal recuperative rest when they go to sleep at their normal time, and wake up at their normal time. Doing otherwise substantially cuts down on the quality and quantity of sleep. We can’t simply “switch ourselves into deep sleep” just because the crew schedulers tell us this is our 10-hr. rest period. Let’s call this strike No. 4.

Then, when the alarm clock jolts you awake in Teterboro — which, by the way, is 1 a.m. on your California body clock — you can be forgiven for reconsidering your career choice. How much deep recuperative sleep did you manage to get? Clearly not enough. Perhaps it was 4 hr. of deep sleep, thus starting day No. 2 with an accumulated 8 hr. of sleep debt. That’s the equivalent of missing an entire night of sleep. Let’s designate the sleep debt issue as strike No. 5.

Changing time zones or operating on the back side of the clock imposes the additional burden of circadian desynchronization. Graeber’s research found that the circadian rhythm system is unable to adjust rapidly to sudden shifts. In effect, the system resists changes in its timing and stability and complete resynchronization of the body’s biological timing system can take several days.

Additionally, resynchronization occurs at a different rate depending on whether the body must adapt to a westbound or eastbound time zone changes. Medical specialists in the field of sleep medicine have determined that, depending on the number and direction of time zones crossed, it can take days for the circadian system to resynchronize. And recovery from eastbound flights is more difficult. The general rule of thumb is that adjustment to eastbound travel requires 1.5 days per time zone crossed. Yet, as pilots it is entirely possible to be in a different time zone each night of a trip. In short, we don’t get days to resynchronize. Circadian rhythm desynchronization is strike No. 6. Two batters down.

There are substantial differences in various people’s ability to adjust to repeated time-zone shifts. “Morning people,” introverts, the elderly and those with stable rhythms have slower rates of resynchronization than others. Furthermore, studies found that crew members over 45-50 years of age experience less total sleep and poorer quality sleep. If you’re in this age group, that’s strike No. 7.

The combination of poor sleep quality on the road as well as trying to sleep at times outside your body’s normal sleep time will worsen the sleep debt during the trip. It comes with the job. NASA research found that air crews tend to accumulate more sleep debt and thus become more fatigued as they progress through a trip.

Does working a pilot hard contribute to fatigue? Yes, it can, but if the pilot is operating during a normal “day” cycle and then has the opportunity to rest during a normal “night” cycle, the average aviator will be able to show up for flight duties the next day adequately rested.

I have asked pilot groups if they would rather work a hard 12-hr. day that begins at 7:30 a.m. or work an 8-hr. day that begins at 5 a.m., and they almost always choose the former. Why? The sleep loss associated with early morning report times is considerable. NASA research found that the timing of flight activities and not necessarily the length of the duty day or the number of segments flown appears to contribute more to fatigue.

You would not be alone if you dread the fatiguing effect of those early report times. (And admit it, how many of us set at least two alarm clocks for those early morning wake-up’s?) An early report time is strike No. 8.

The British Association of Airline Pilots, together with the University College London Psychobiology Group, carried out a survey of fatigue and well-being among British airline pilots. The study revealed that sleep problems are correlated with fatigue. As a consequence, fatigue can become self-perpetuating. It determined that “Pilots may eventually end up in the vicious circle of being too tired to adequately rest or sleep, which in turn will leave them even more exhausted.” (See the “How Bad Is the Problem?” sidebar.)

Dr. David Gozal, both a professor at the University of Chicago School of Medicine specializing in sleep disorders and a deputy editor of the journal Sleep and Frontiers in Neurology, found that recovery from sleep loss does not immediately restore all of the body’s systems. Neural and metabolic activity take much longer to recover. “Recovery is not so simple,” he found, adding, “If you accumulate debt, there will be compounded interest and an uphill battle to recover.”

Up to this point I have not touched on pilot duties in a typical day, the stresses involved, and the fatigue-inducing conditions under which we work. A 6 a.m. show in January for clients who enjoyed a weekend of skiing at a ski resort means you are likely walking out to an aircraft that has been cold-soaked to -20F on the ramp for maybe the last three days. Preflighting such an aircraft on a still-dark morning in the mountains can be breathtakingly unkind. Conversely, getting an aircraft ready for a post-maintenance inspection flight on an August afternoon with the ramp radiant temperature spiked at 120F will spike crew fatigue levels as well.

Let’s say your departure is from New York’s Westchester County Airport (KHPN) on a Friday afternoon with weather all around when your lead passenger shows up with an additional golf buddy for the trip to Bermuda. Suddenly, you have additional customs paperwork to file as well as new weight and balance to calculate that could cause a cascading set of changes on your loading and fuel. Naturally, the principal expects the engines to start turning as soon as he steps aboard and to be rolling within minutes, oblivious to the considerable stress imposed on the crew. Entering New York airspace at that time and day along with foul weather guarantees a high workload environment for the departure with controllers issuing nonstop instructions as they try to keep the metal moving. You will not really catch your breath until climbing through FL 300.

The view from the flight deck at FL 410 on a clear day is one we would never trade, but the cockpit itself contributes to fatigue. Sitting confined in small seats for long hours induces lethargy, as well as our chances for developing deep vein thrombosis, or DVT. The dry, pressurized air is wicking away precious volumes of our body’s moisture, thus causing us to be in a chronic state of dehydration for most of our hours airborne. Glare, vibrations and noise all increase fatigue. How much does the combined effect of these add up? The anecdotal evidence suggests it is considerable. (See the “Cockpit Environment and Fatigue” sidebar.)

Despite the forging, most of us are Type A personalities who seek out challenges and enjoy the sense of doing a job well. So, as a group, we are not very good at stepping away from the plate and saying, “Coach, I need to sit this one out.”

In the words of Steven R. Hursh Ph.D., chief scientist of the Institutes for Behavior Resources, “There’s no breathalyzer for tired . . . but there should be.” Absent a practical real-time fatigue detector, he says most people underestimate just how tired they are and how impaired they are by that fatigue. 

Admonishments to “be more professional” or “show attention to detail” ignore the underlying pervasiveness of serious fatigue among line pilots. Professional aviators will continue to be warned to use their rest period productively, even though the scientific evidence is plentiful that the human body simply does not flip a switch at 6, 7 or 9 p.m. to begin deep recuperative sleep in preparation for a 3 a.m. report for duty the next day. It is the timing of sleep, not the amount of time awake or “in rest,” that is the critical factor controlling sleep quality.

The facts about fatigue are clear, and something to sleep on. 


Related Articles


As a subscriber to one of Aviation Week Network’s market briefings, your searches only provide you with access to articles from within that product.

To find out about obtaining additional data – including the most comprehensive details on organizations, fleets, personnel and programs – click here or call +1.561.279.4661.


As a subscriber to one of Aviation Week Network’s market briefings, your searches only provide you with access to articles from within that product.

To find out about obtaining additional data – including the most comprehensive details on organizations, fleets, personnel and programs – click here or call +1.561.279.4661.


As a subscriber to one of Aviation Week Network’s market briefings, your searches only provide you with access to articles from within that product.

To find out about obtaining additional data – including the most comprehensive details on organizations, fleets, personnel and programs – click here or call +1.561.279.4661.


As a subscriber to one of Aviation Week Network’s market briefings, your searches only provide you with access to articles from within that product.

To find out about obtaining additional data – including the most comprehensive details on organizations, fleets, personnel and programs – click here or call +1.561.279.4661.