14 CFR 135.267: what the duty time rules actually say

14 CFR 135.267 is the federal regulation that governs how long a Part 135 flight crew can be on duty, how long they must rest between duty periods, and how many flight hours they can accumulate over rolling time windows. It is one of the most operationally important regulations in charter — and one of the most frequently misread.

What the rule covers

Section 135.267 sets four distinct limits that all apply simultaneously to any Part 135 crew member:

1. Cumulative flight time caps — 500 hours in any calendar quarter, 800 hours in any two consecutive calendar quarters, and 1,400 hours in any calendar year. These are hard ceilings, not targets. (135.267(a))
2. Flight time within a duty period — 8 hours for a single-pilot operation, 10 hours for a two-pilot operation. (135.267(b))
3. Scheduled duty period length — the default maximum is 14 hours. (135.267(c))
4. Rest requirements — a minimum of 10 consecutive hours off duty between duty periods. (135.267(d))

The 14-hour duty period

A scheduled duty period is the total elapsed time from sign-in (showtime) to release. The 14-hour limit means the operator cannot schedule a crew member for more than 14 hours of continuous duty. Unforeseeable delays may push the actual elapsed time beyond 14 hours — 135.267(c) allows this provided it was not foreseeable at the time of scheduling — but the crew member cannot be scheduled for more than 14 hours.

An important nuance: the duty period does not reset at midnight. It runs from actual showtime to actual release, regardless of calendar day. A crew who signs in at 22:00 and is released at 11:00 the next day has been on duty for 13 hours — legal, but close.

The 10-hour rest minimum

After a duty period ends, the crew member must receive at least 10 consecutive hours of rest before beginning another duty period. This is a floor, not a target. A crew released at 23:00 cannot show up until 09:00 the next day.

The 10 hours must be consecutive. Split rest does not count. And the clock starts at actual release, not at when the crew arrives home.

The 8-hour absolute floor (reduced rest)

Section 135.267(d) includes a reduced rest provision: with prior authorization from the certificate holder, the rest may be reduced to 8 consecutive hours. The catch is that the full 10-hour rest must be provided before the next duty period after the reduced-rest period. You can take the short rest once; you cannot chain it. (See our detailed post on reduced rest.)

Cumulative flight time: the math

The quarterly and annual caps are rolling, not calendar-fixed in the way a layperson might assume. “Any calendar quarter” under 135.267(a)(1) means the four three-month blocks Jan–Mar, Apr–Jun, Jul–Sep, Oct–Dec. “Any two consecutive calendar quarters” means the four possible pairs of adjacent quarters.

The practical effect is that a pilot who flies 499 hours in Q3 and 301 hours in Q4 is at 800 for the two-quarter window — exactly at the limit. A dispatch tool that only checks the current quarter misses this.

How Clearspar applies 135.267

When you build a quote in Clearspar, the compliance engine checks all four limits simultaneously for the proposed PIC and SIC:

• It loads actual duty entries from the logbook to compute cumulative hours.
• It checks flight time within the proposed duty period against the 8-/10-hour limit.
• It verifies the rest gap between the last duty entry and the proposed showtime.
• If your GOM has stricter limits than the FAR, those are applied instead.

An UNABLE result with the 135.267 citation is the gate working as designed. The finding includes which limit is violated and by how much, so the dispatcher can decide whether to adjust the schedule, swap crew, or issue an operator override (which is logged and shows up on the dispatch release).