Crew rest is a critical part of airline flying. Airlines, charter companies, and even flight schools have limits on how much their crews can work before taking mandatory time off. Though sometimes convoluted – and inconvenient if a flight cancels because pilots run out of time – these rules are crucial to ensuring flights, and the National Airspace System as a whole, continue to operate safely and efficiently 24 hours per day.

Fatigue, historically, has been a contributing factor to a number of aviation incidents and accidents. Fatigue degrades decision-making, alertness, and reaction times, making it more difficult for pilots and other air crew to recognize and respond to critical situations in flight.

Crew Rest Overview

The rules that dictate required rest periods are significant factors in determining how and when airlines schedule their flights. They need to make sure not only that the pilots and cabin crew won’t fly too much but also that they won’t be at the airport for extended periods. That is because crew rest is not determined based on flight time; rather, it’s based on duty time, beginning the moment that the crew arrives at the aircraft to begin their inspections and paperwork.

Crew rest limitations vary based on the type of operation that crews are operating under. Major airlines operate under Part 121 of the Federal Aviation Regulations (FAR), while charter companies operate under Part 135. Private operators, such as non-aviation companies that use pilots to further their own business, can operate under Part 91 of these regulations. 

Mandatory rest requirements depend largely on how long a crew’s duty time was in a certain day. Longer days require more rest before crews need to show up to work again.

As a baseline, crews cannot be scheduled with any less than eight consecutive hours of rest at a time. This allows sufficient time to leave the airport, go to a hotel, sleep, and return. There are further rest requirements for days that crews are scheduled to work especially long hours.

Crew Rest for Commercial Airlines

Under Part 121, nine hours of rest are required if a crew member is scheduled for under eight hours of flying time. That requirement increases to 10 hours for 8-9 hours and 11 hours for 9+ hours of flying. Companies may not schedule crews to operate flights unless they have met at least this minimum rest requirement. There are some exceptions to this rule if the crews are offered extended rest at the end of a certain duty period.

This is a critical reason why international flights have multiple pilots: with more than two pilots, a flight deck can be fully-staffed for longer by allowing some pilots to rest mid-flight. The same is true for flight attendants onboard, who are equally subject to rest requirements.

When crews are on their mandatory rest, they may not be scheduled to accept any duty assignment. 

Important to this rule is that non-local commuting is not allowed to be part of a rest period. Since many crewmembers do not live in the cities where they are based, they must be scheduled for additional time off in between trips to allow for travel home and back to base.

Ultimately, Part 121 crewmembers are limited to a certain amount of flight time per week, month, and year, further limiting the amount of work they can accept. An important distinction is between acute and chronic fatigue. Acute fatigue is that which happens over a short period due to lack of sleep, hunger, or dehydration; chronic fatigue is a long-term condition resulting from consistent stress or sleep deprivation.

By limiting both the amount of time crews can fly in a day as well as the amount they can work over a longer period, the FAA strives to ensure that crews cannot burn out over long periods even if they get enough rest day-to-day. Such prevents fatigue symptoms that are more difficult to notice long-term but can still be hazardous.

Crew Rest for Charter Pilots and Instructors

Part 135 charter crews equally have rest requirements, though they are not quite as strict as the Part 121 rules. The same eight hour rest baseline still exists, as do the longer rest requirements for longer duty days. However, Part 135 pilots are allowed to work more hours in a week, month, and year than Part 121 pilots are, allowing for more consistent utilization long term.

The rules change again for Part 135 crews working non-scheduled operations: single-pilot operations are limited to eight hours of flying per day, while multi-pilot crews get 10. These pilots have more exceptions regarding when they are allowed to extend their duty days granted enough rest is provided in between, and they are allowed even more annual flight hours than even scheduled Part 135 pilots. If inflight delays cause crews to exceed their duty times, extended rest must subsequently be provided.

Pilots operating under Part 91, the set of regulations governing general operations, are limited only if they fly for companies under Parts 121 and 135 as well. Many aircraft ferry companies operate exclusively under Part 91, allowing their pilots to fly for extended periods nonstop in order to meet delivery schedules.

Flight instructors, meanwhile, are limited to eight hours of in-flight instruction at a time. There is no limit to how much they can provide ground instruction on top of those eight hours. Note that there is no rest requirement in this rule, only a maximum flying requirement. Flight instructors also have no annual maximum – outside of eight hours per day every day, of course. They are also not prohibited from flying in non-instructional capacities in their time off.

Repercussions for Violating Crew Rest

Crew rest is, more than anything, built to protect the traveling public. Essentially, the more public the operation, the more rest is required for each crew member. 

Airlines around the world have been fined for violating crew rest requirements; Air India was fined earlier this year for violating crew rest rules, and a Virgin Atlantic pilot was terminated earlier this month when it was discovered she held a second pilot job to circumvent rest rules. The FAA has taken action against airlines violating crew rest regulations for years.

Crew rest violations are easiest to notice in the larger air carrier operations. They are often tougher to notice in Part 91 operations and in flight instructors, who generally have less day-to-day oversight from the FAA or designated representatives. However, when crews do receive inadequate rest, the results are often incredibly public; as with other safety issues in aviation, it only takes one incident to garner attention and bring about substantial change.