By Dr. Leo Hattrup, FAA Medical Officer
Over the years, I have talked to numerous pilots who have flown past a fix, missed calls from ATC, or felt startled to wake up after being asleep for seconds to minutes. A colleague relayed an experience as a military co-pilot. He was on a low-level patrol mission with four other crew members. “I woke up and sheepishly looked around only to discover that I was the only one awake.” I personally have had the opportunity to nudge my safety pilot awake while shooting practice approaches with high terrain on both sides.
While fatigue often leads to just minor errors, it can also be catastrophic. The National Transportation Safety Board (NTSB) has cited fatigue as a causal or possibly contributory factor in multiple mishaps. Prominent examples include American International Airways Flight 808 on August 18, 1993, ValuJet 592 on May 11, 1996, and FedEx Flight 1478 on July 26, 2002. In each accident, the aircraft was destroyed. Everyone on the ValuJet flight perished. The NTSB believed that fatigue contributed to these accidents, affecting aircrew or maintainers.
Fatigue is a broad, subjective term that can refer to both mental and physical impairment often perceived as a lack of “energy.” We focus here on mental fatigue associated with cognitive and performance impairment. Pilots are at risk for poor concentration and easy distraction, task saturation, decreased alertness and attention, slowed reaction time, poor judgment and memory, and emotional lability. The latter manifests itself by impulsivity, irritability, aggressiveness, and anger. In the long term, mental fatigue can lead to depression, insomnia, apathy, and isolation.
Inadequate sleep frequently causes fatigue. It can stem from simply pushing oneself too hard, circadian rhythm disruptions from shift work or trans-meridian travel, stress (at work or home), recreational/extracurricular activity, or ongoing sleep disturbances such as being the parent of a young or ill child. However, fatigue can also be both an initial manifestation of medical problems and a persistent symptom if not adequately treated. Infections, including influenza and COVID-19, can present with fatigue, as can many medications. Chronic illnesses such as endocrine disorders (including hypothyroidism and diabetes), anemia, depression, substance abuse, cancer, infection (hepatitis/HIV/tuberculosis), and sleep apnea can all initially present as fatigue.
We are poor judges of our own fatigue level. Like hypoxia, the condition impairs our ability to recognize its presence. We should trust the input from others and from our own warning symptoms. If you don’t know them, a spouse, family member, or close friend probably does.
Pilots, in general, tend to be motivated to overcome challenges despite difficulty. The solution is to take a break and rest. Ask this question: “If I am too busy to stop, do I have time to do it over?” Sometimes there is no do-over option.
While treatment for fatigue is often very simple to describe, it can be difficult to execute. Recognize that no one is immune. Caffeine and other stimulants can mask symptoms but do not cure fatigue or sleep debt. Get adequate sleep and exercise, treat any underlying medical issues, and know when to say no. Luck should not be part of the planning process.
⚕️ FAA Safety Video: “Grounded — A Story of Fatigue”
⚕️ FAA TV: Fatigue in Aviation
⚕️ AC 120–103A, Fatigue Risk Management Systems for Aviation Safety (PDF download)
⚕️ FAA Fatigue Risk Management: www.mxfatigue.com
⚕️ FAA Fatigue in Aviation Brochure (PDF download)
Leo M. Hattrup, M.D., received a bachelor’s degree from Wichita State University, a master’s in public health from Harvard University, and a doctorate from Vanderbilt University. He is retired from the U.S. Air Force, in which he spent the majority of his career in aerospace medicine. He is board-certified in aerospace and occupational medicine. He is a certificated flight instructor and enjoys flying airplanes, helicopters, and gliders.