AoC number


Primary domain


Secondary domain



Air traffic controller fatigue is an even more widespread and serious issue than flight crew fatigue. ATCO working hours led to various cognitive performance degradations associated with sleep deprivation and working at times for which humans are not biologically programmed. However, when considering safety, the impacts of fatigue are less clear, as they are influenced by our own awareness of our state and by our ability to develop strategies to overcome the detrimental effects of fatigue. Therefore, the prevention of the negative safety outcomes linked to fatigue should make it possible to reduce the occurrence of fatigue with appropriate scheduling, but also by providing ATCOs with the means to detect and mitigate its effect.

Prior to 2015, air traffic controllers regularly worked the “Rattler” schedule, with five consecutive eight-hour shifts (with eight-hour breaks in between) and three-day weekends. NASA and the FAA studied its impact on performance, but refused to reveal the results of the study for four years. The Rattler was revealed to produce considerable fatigue among air traffic controllers, with many getting only 5.8 hours of sleep per day (3.1 on midnight shifts). Two in ten controllers made significant errors in the preceding year, and half attributed those errors to fatigue. Why NASA and the FAA withheld the information for so long is unknown.
Fatigue has been on the National Transportation Safety Board (NTSB) “Most Wanted List” since the initial list in 1990. Warning signs can include drowsiness, lack of communication, and requests for easier roles. Sleep is the best solution, even for night-shift employees; other measures merely act as stop-gaps.

Potential hazard

  1. Increased frequency of Operational Errors: An occurrence attributable to an element of the air traffic control system in which:
  2. Less than the applicable separation minima results between two or more aircraft, or between an aircraft and terrain or obstacles; or
  3. An aircraft lands or departs on a runway closed to aircraft operations
  4. Impaired performance: delayed, erroneous or chaotic responses to normal stimuli
  5. Reduced ability for the controller to process complex information and cope with the unexpected. It is when the automation fails or evidences unexpected behavior that the human needs to step in. Fatigue dramatically compromises the ability of the flgith crew to perform as needed in off-nominal conditions.
  6. Automation mode confusion.
  7. Reduced alertness
  8. Adverse physiological consequences: stressors affecting alertness
  9. Adverse effects of long commutes on performance
  10. Reversions to “fight-or-flight,” panic or freeze instinctive self-preservation behaviors in emergency situations; reflexive response to stimulation
  11. Failure to report errors and omissions arising from fatigue that do not necessarily result in reportable incidents
  12. Poor environmental characteristics of rest areas in air traffic control facilities
  13. A recent FAA Office of Inspector General report found that pilots might not be reporting all instances of fatigue. The report noted that, of 33 air carrier pilots interviewed by OIG researchers, 26 (79 percent) said that, at some time, they had been fatigued while on duty; nevertheless, only eight pilots notified their air carrier of their condition. Among the reasons cited for not reporting fatigue was the fear of “punitive action from their employers.”

Corroborating sources and comments

Human Performance and Fatigue Research for Controllers (PDF), Source: Mitre Corporation;

Controller Operational Performance Effects

ASRS Analysis study (spanning 1988-1996)–2.7% of reports referenced controller-related fatigue

OEDS database study–80% of OEDs between 0800-1900; nearly 50% of errors occurred within 30 minutes on-position, usually upon returning from a break

Higher percentage of data posting errors occur on midnight shift

Neither study revealed shift work variables as strong predictors of the severity of operational errors

NTSB (2007) – present case studies of fatigue related incidents/accidents (Prior to 2015, air traffic controllers regularly worked the “Rattler” schedule, with five consecutive eight-hour shifts [with eight-hour breaks in between] and three-day weekends. NASA studied its impact, but kept the results closed off until August 2015, where it turned out that the Rattler drastically increased controller fatigue.) (Guide to dealing with fatigue for air traffic controllers. Drowsiness, lack of communication, and requests for easier roles are all warning signs. Sleep is the best solution, even for night-shift employees.) (An elaboration on the infamous air traffic controller study. Nearly two in ten controllers made significant errors in 2010, the year before the study was conducted, and half attributed those errors to fatigue. Controllers only had 5.8 hours of sleep per day, and 3.1 on midnight shifts. The “most tiring schedules” entailed “five consecutive midnight shifts”. The FAA not only refused to share the report, but kept quiet on possible fixes.)

Last update