Overview of FAR Part 135 Rest Rules
Unlike scheduled airlines operating under Part 117, unscheduled on-demand charter operations operate under the older, rigid rules of Subpart F (135.261 to 135.273). The overarching principle is to ensure pilots are not flying while exhausted.
The regulations define absolute ceilings for commercial flight time and mandate specific blocks of uninterrupted rest. Any time spent working for the company—even ground duties like loading bags or doing paperwork—is considered duty time and eats into the pilot's available window before they must enter legal rest.
The 24-Hour Look-Back Rule
The most confusing aspect of Part 135 is the 'rolling 24-hour window'. The FAA requires that at any exact moment during a flight, you must be able to look back 24 hours and find a legal rest period.
This means you cannot simply schedule a pilot for an early morning flight on Monday, give them the afternoon off, and fly them late Monday night, if the combination of those flights pushes them past the limit without a 10-hour rest block in between.
How to Calculate Required Rest Periods
For single-pilot or standard two-pilot crews on unscheduled operations, the base flight time limit is 8 hours for a single pilot, or 10 hours for a two-pilot crew, within a given duty period. If these limits are exceeded due to unforeseen operational circumstances (like ATC holds or weather deviations), compensatory rest must be granted.
The Rest Tiers: If a pilot flies legally but exceeds the scheduled time due to weather: Exceeding up to 30 minutes requires 11 consecutive hours of rest. Exceeding by 30 to 60 minutes requires 12 hours of rest. Exceeding by more than 60 minutes requires 16 hours of rest.
Worked Example: A two-pilot crew is scheduled for 9.5 hours of flight time. Due to severe thunderstorms, they are held in a holding pattern and ultimately log 10.4 hours of flight time. Because they exceeded their 10-hour limit by 24 minutes (less than 30 mins), their normal required 10-hour rest period is legally extended to 11 hours before they can report for duty again.
Calendar and Rolling Flight Time Limits
In addition to daily rest requirements, Part 135 imposes long-term caps to prevent chronic cumulative fatigue.
A pilot may not exceed 500 hours of commercial flight time in any calendar quarter, 800 hours in any two consecutive calendar quarters, or 1,400 hours in any single calendar year. Furthermore, they must receive at least 13 rest periods of at least 24 consecutive hours in each calendar quarter.
Frequently asked questions
What counts as 'Rest' under Part 135?
Rest must be prospective and completely free from all restraint or duty. If the chief pilot calls the resting pilot to discuss the next day's schedule, the rest period is legally broken and the 10-hour clock starts over.
What happens if a flight is delayed on the ground?
Ground delays count as duty time, but not flight time. However, if the ground delay pushes the pilot so deep into their duty day that they cannot complete the intended flight time before requiring their legal rest period, the flight must be cancelled or a fresh crew swapped in.
Are empty repositioning flights (Part 91) counted toward flight time limits?
Yes. While flying an empty airplane is technically operated under Part 91 rules, all commercial flying performed on behalf of the certificate holder counts toward the Part 135 daily and quarterly flight time caps.
Can a pilot waive their rest requirements if they feel fine?
No. The FAA rest requirements are federal law. Neither the pilot nor the operator has the authority to waive them, regardless of how rested the pilot claims to be.