Many people are aware of minimum crew rest periods. Whether it’s through a connection in the industry, an experience where a delay lead to the crew timing out, or a story about such an experience, crew rest periods in Part 121 (and Part 135) flying have proved a critical piece of travel for many.

Minimum pilot rest requirements have been around since the 1960s, and flight attendants got their own duty time limitations in the 1990s. The pilot rules were updated in 2011 with a two-year implementation period, and cabin crews won protections for mandatory 10 hour rest periods in 2022.

Federal Minimum Rest Regulations

Most people’s understanding of minimum pilot duty time are along the lines of “pilots must get 8 hours of rest in a day.” However, the rest requirements are quite a bit more nuanced than that.

It’s important to distinguish between the three pilot rest requirements: the Part 121 requirement for all flight crewmembers, the Part 135 requirement for unscheduled one- and two-pilot crews, and the Part 91 requirement (yes, part 91 has a minimum crew rest requirement).

For our readers who are not intimately familiar with the regulations governing aviation, Part 121 deals with scheduled air carriers (companies like American Airlines, United Airlines, Delta Air Lines, etc). Part 135 (generally speaking) unscheduled charter flights plus a limited type of scheduled flying. Part 91 is general operating and is the regulations chapter a large majority of small propeller planes use.

Let’s recap all three regulations. The air carrier regulation governing all the airlines a casual reader is familiar with is easy to understand. 14 CFR § 121.471 outlines that no flight crew may fly without:

• 9 consecutive hours of rest for less than 8 hours of scheduled flight time
• 10 consecutive hours of rest for 8 or more but less than 9 hours of scheduled flight time
• 11 consecutive hours of rest for 9 or more hours of scheduled flight time.

14 CFR § 135.267, which governs crew rest for the charter operations, outlines that flight crew must receive:

• 8 hours for a flight crew consisting of one pilot; or
• 10 hours for a flight crew consisting of two pilots qualified under Part 135 for the operation being conducted

However, Part 135 pilots may exceed these flight limits if:

• Their assigned duty period is no more than 14 hours
• Those 14 hours are immediately preceded by and followed by a required rest period of at least 10 consecutive hours of rest; and
• The cumulative amount of commercial flying they do does not exceed 8 hours for a flight with one pilot and 10 hours for a flight consisting of two pilots. 

There are additional rest requirements when a pilot under Part 135 exceeds their duty time. The important thing to know for those is that if a Part 135 pilot exceeds their maximum duty time regulations, there are extended crew rest limitations before they can be on duty again.

And the Part 91 duty time requirement. This requirement pertains to aircraft operating Part 91 that are managed by an operator of some kind. This covers a wide variety of situations, but one notable situation is when an air carrier operates an aircraft repositioning flight under Part 91 to move it to an airport where maintenance is performed or a scheduled flight will originate. 14 CFR § 91.1059 dictates that, during any 24 consecutive hours, the total flight time to a crew may not exceed:

• 8 hours for a flight crew consisting of one pilot; or
• 10 hours for a flight crew consisting of two pilots qualified under Part 91 for the operation being conducted.
• 14 hours of total duty time

The minimum rest requirement increases after a duty period involving multi-time-zone flights: the minimum rest time goes from 10 hours to 14.

Legal Applicability

The common theme between all three regulations is that they apply to pilots who have some connection to commercial flight operations. That means that hobby pilots have no minimum rest or maximum duty time requirements (and that, though it likely very rarely happens, there is nothing stopping commercial pilots from going to fly general aviation for hours without interfering with their minimum commercial rest requirements).

That does not mean, of course, that general aviation pilots should not think about minimum rest requirements at all. In fact, just that there are no minimum rest requirements – and no flight department managers looking over their shoulders – means that general aviation pilots can be even more creative with their rest requirements than airline pilots.

An Overview of Personal Minimums

Every pilot, whether they are a commercial pilot or a lifetime hobby pilot, is intimately familiar with the concept of “personal minimums.” These are guidelines above and beyond the legal flight minimums for certain operations that define which conditions a pilot feels safe flying in and the concrete limitations that will define which conditions will cause them to cancel a flight.

Personal minimums should cover a wide range of issues, such as weather conditions, physiological states, or mental dispositions. A visual-only pilot may say, for example, that even though the minimum cloud height for visual flight is 1,000,’ that they will not fly unless the minimum cloud ceiling is at least 3,000’ above the ground.

All this to say: fatigue is an oft-overlooked aspect of personal minimums. It is included in the famous IMSAFE checklist that all pilots are familiar with, but it is easy for a pilot to wave it off by saying “I got enough rest; I can feel it”…after downing three cups of coffee in a row and assuming that their caffeine high will both solve all their fatigue problems and last forever.

However, fatigue is among the most insidious threats pilots face. The FAA’s own training materials highlight that pilots may be completely unable to notice signs of fatigue in themselves until they start making massive errors, by which point their control is already clumsy, their thinking slow, and their coordination deteriorating. These are all conditions that could prove incredibly hazardous if an emergency situation arises that pilot notices late and has more difficult handling, or if they encounter a challenging situation like a sudden encounter with instrument meteorological conditions at night.

Establishing Personal Minimums

Therefore, pilots need to go beyond determining whether they feel ok to fly. As with other personal minimums, pilots should use concrete minimums to define whether they’ve gotten enough rest. The regulations we’ve already outlined (§ 121.471, § 135.267, and § 91.1059) are great starting points. Pilots should try to emulate these regulations; after all, if they’re good enough for professional airline pilots, why aren’t they good enough for general aviation pilots?

However, just like with personal minimums in other situations, pilots should not feel limited to these regulations. If a pilot finds that they in fact need more rest than outlined (maybe they need 8-10 hours of sleep instead of just 8-10 hours of “rest” before flights), they should not hesitate to implement the change.

Further, an additional personal limit might be to say that the pilot will take additional rest in between flights on a single trip. A student pilot completing a 150 NM solo cross country for private pilot certification or a 300 NM solo cross country for commercial pilot certification might stop at each airport they land out to stretch their legs, use the bathroom, have a snack, and recoup for the next segment of their flight. By allowing themselves to de-stress in between each flight, they can de-stress and keep themselves alert for longer since they don’t need to be sharply focused for hours at a time.

Rest Before Duty Time

It is also important to notice that many of the rest requirements in the regulations above list the minimum rest requirements between duty times, not flight times. That means that the clock runs, loosely, from when the pilot leaves the airport one night to when they arrive back the next morning. This is not a question of needing 8 hours from when the wheels touch the pavement on one flight to when they lift off on the next; it’s a question about rest between finishing the post-flight checks one day to starting the pre-flight inspection on the next.

This is another aspect that private pilots must integrate themselves. Don’t just think about how fatigue impacts your flying ability. Consider how it affects your ability to notice discrepancies on your preflight inspection and your ability to properly secure the airplane for the night. All of these items affect the airworthiness of your aircraft and therefore the safety of your flight.

Fatigue Has Many Sources

And pilots should not forget about how other aspects of life impact fatigue. Stress is an especially-critical factor that affects fatigue levels. A pilot may get more tired out dealing with stress than they do without it, so if a pilot knows that they are stressed about something outside of flying, they must increase their rest requirements before and during flights.

The same argument could be made about particularly-challenging flights. The energy demand on a pilot is a lot different on a rural VFR cross country on a bright, cool, clear fall morning to get Sunday brunch versus on a blistering-cold flight in hard IMC. A pilot must be aware of the mission ahead of them and determine if they have enough rest not only to fly but to handle the specific mission ahead of them.

“I can tell you firsthand that well-rested crew members are important to safety,” said acting FAA administrator Billy Nolen, a former airline pilot, in October 2022. This sentiment relates not only to professional pilots but to the casual flyers that share the national airspace system, use the same airports, and in some cases operate in relatively-close proximity to commercial aircraft in busy terminal areas.

Fatigue impacts every aspect of a pilot’s ability to operate an aircraft safely. Do not let it impact your flying in a detrimental way. Using concrete personal minimus about the amount of rest you will get before flights and the amount of rest you will take on long trips is critical to your safety and should not be taken lightly.

Pilots must always give themselves every possible opportunity to succeed. Think of the saying to “use all available resources.” The same sentiment applies to rest: use each available opportunity to keep yourself alert and focused on the task at hand to assure the safe completion of your flight.

Editor’s Note: Welcome back to the Private to Professional series. Each week, we will take time to break down a new regulation written for professional pilots in Part 121 and Part 135 flying, and we will consider different ways to apply those regulations to general aviation. Some regulations have straightforward applications to general aviation, but there is usually more that meets the eye. Thus, we will take time to explore a wide variety of ways general aviation pilots can apply even simple things, like minimum rest requirements, to their own flying. Check back in next week for the next installment of the series. Read last week’s article here.