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Going Long — The Physiological Risks of Fatigue

FAA Safety Briefing
Cleared for Takeoff
4 min readSep 1, 2022
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By Dr. Susan Northrup, FAA Federal Air Surgeon

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Dr. Susan Northrup, FAA Federal Air Surgeon

As I write this article, I am catching up from AirVenture. This wonderful experience tends to be very busy so fatigue is very much on my mind and I suspect that it is for many of you. In general, we think of fatigue as acute (recent sleep deficit), chronic (multiple days of inadequate sleep), or circadian (related to time of day and normal physiological lows). In commercial aviation, there are specific safeguards to limit the duty day depending on reporting time and number of legs. These regulatory restrictions do not apply to operations under 14 CFR part 91, but our physiological limitations do. The number of mishaps attributed to fatigue, some fatal, clearly demonstrates this.

Fatigue impairs the brain’s executive functions including attention, multitasking, and decision-making, sometimes dramatically. This can result in confusion, task fixation, increased errors and, of course, drowsiness. Unfortunately, your ability to recognize this is also impaired.

Early in training, we are more likely to dedicate time specifically to flying, whether local or cross-country. Both tend to focus on meeting explicit regulatory requirements (hours and distance). This makes sense in flight training; the goal is to learn essential aviation skills as efficiently as possible. But this approach might not prepare you for your first actual long-range solo or sole pilot flight without someone reviewing your planning. Tack on fatigue and you increase the risk of an adverse outcome.

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Here are a few potential pitfalls. The risk of fatigue should be obvious when you experience inadequate sleep, trans-meridian travel (jet-lag), recent illness, hectic work week, etc., but it’s unwise to underestimate human ability at self-deception. Even if you had enough time for sleep, it might not have been restorative. Stress, alcohol (even within legal minimums), some medications, or a poor sleeping environment, can lead to unexpected (and unrecognized) fatigue. Even the flight can contribute: preparations, duration of flight at altitude, weather, or unfamiliarity with the course are all aggravating factors. Also dehydration can mimic and magnify the effects of fatigue.

What Can You Do?

A pre-flight and ongoing self-assessment of your fitness is critical. IMSAFE is a good tool. Pressing ahead if you feel tired is high risk, especially at night. Take a nap, reschedule the flight, or break up your trip with an overnight stay. Stay hydrated even if it requires an en route stop. For longer flights, plan shorter legs. It helps keep a safe fuel reserve, a comfortable bladder, and reduces the risk of a blood clot. (By the way, coffee is not the solution: it does not replace adequate rest). It is better to arrive safely at your destination late than not at all.

What Are We Doing?

Aerospace medicine conducts ongoing research into fatigue management and countermeasures. My staff are working with counterparts at NASA and NTSB to continue steady improvements in flight safety. Robust programs for commercial aviation can be applicable to general aviation, even for single pilot operations (see below). For over a decade, general aviation has enjoyed a steady decrease in the mishap rate. Please help keep this trend going downward.

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Dr. Susan Northrup received a bachelor’s degree in chemistry, a medical degree from The Ohio State University, and a master’s degree in public health from the University of Texas. She is double board-certified by the American Board of Preventive Medicine in Aerospace Medicine and Occupational Medicine. She is a retired U.S. Air Force colonel and a former regional medical director for Delta Air Lines. She is also an active private pilot.
This article was originally published in the September/October 2022 issue of FAA Safety Briefing magazine.



FAA Safety Briefing
Cleared for Takeoff

Official FAA safety policy voice for general aviation. The magazine is part of the national FAA Safety Team (FAASTeam).