Legal Interpretations
Hryniw 2014
Summary
The Question
Under 14 CFR part 117, what is the difference between a reserve availability period and a flight duty period?
Background
A requester asked the FAA to explain the difference between a reserve availability period (RAP) and a flight duty period (FDP) under the 14 CFR part 117 flight, duty, and rest rules.
The FAA’s Interpretation
An FDP is more flexible but more tightly limited. A RAP is short-call reserve during which the crewmember must be available for an FDP assignment, and its 14 CFR 117.21(c) length limits are generally less stringent. Requiring flight turns it into an FDP, and requiring airport presence turns it into airport/standby reserve. An FDP permits any duty, including flying, but faces the limits of 14 CFR 117.13, 14 CFR 117.17, and 14 CFR 117.23.
- Requester
- Hryniw
- Issued
- August 8, 2014
- Subjects
- General Operating & Flight Rules · Air Carrier & Commercial Operations · Flight & Duty Time
Regulations Cited
Page 1
U.S. Department
of Transportation
Federal Aviation
Administration NJQ ."" 8 .2014
Taras Hryniw
Dear Mr. Hryniw,
Office of the Chief Counsel 800 Independence Ave., S.W.
Washington, D.C. 20591
This is in response to your May 19, 2014 letter asking about the difference, under 14 C.F.R. patt 117, between a reserve availability perjod (R,AP) and a flight duty period (FDP).
Part 117 contains a set of flight, duty, and rest regulations that apply to all part 121 passenger operations and certain part 91 operations. 1 Those regulations govern, among other things, the RAP and an FDP that a flightcrew member can work. A RAP occurs when a tlightcrew member is placed on short-call reserve. Part 117 defines a reserve availability period as "a duty period during which a certificate holder requires a flightcrew member on short call reserve to be available to receive an assignment for a flight duty period. "2 The RAP ends when a fligbtcrew member is either released from the RAP by the certificate holder or assigned to an FDP. The length of the RAP is governed by the limits specified in§ 117.21(c), and those limits are generally less stringent than the limits governing the length of an PDP.
In exchange for the less-stringent limits on the length of the RAP, a flightcrew member is more limited in the activities that he or she can engage in during the RAP. Specifically, a flightcrew member cannot be required to fly an aircraft duriD.g a RAP without transfo1ming the RAP into an PDP. A flightcrew member on a RAP cannot even be asked to be located at an airport during the RAP, as this requirement would transform the :flightcrew member's short-call reserve into airport'standby rescrve. 3 An PDP occurs "when a flightcrew member is required to report for duty with the intention of conducting a flight, a series of flights, or positioning or ferrying flights ... "4 In contrast to a RAP, a flightcrew member on an FOP can be assigned to any type of duty, including flying an aircraft, by the certificate holder. However, in exchange for this flexibility, the length of an FDP is subject to the more stringent daily and cumulative FDP limits of§§ 117.13, 117.17, and 117.23.
1 14C.F.R.§117.1.
2 14 C.F.R.§117.3.
3 See id. (definition of Airport/standby reserve).
Page 2
Thus, to sum up, the difference between a RAP and an FDP under part 117 is that an FDP provides more flexibility than a RAP, but the length of an FDP is more stringently limited than the length of a RAP.
We appreciate your patience and trust that the above responds to yom concerns. If you need further assistance, please contact my staff at (202) 267-3073. This response was prepared by Alex Zektser, Attorney, International Law, Legislation, and Regulations Division of the Office of the Chief Counsel, and coordinated with the Air Transportation Division of Flight Standards Service.
ark W. Bury -nAssistant Chief Counsel for Y International Law, Legislation, and Regulations, AGC-200
Regulations Referenced
Snapshot retrieved August 6, 2026.