Source:
https://www.federalregister.gov/arti...t-requirements

vi. Assigning an FDP

A4A and Alaska Air asked whether a rest period that is longer than the regulatory minimum could be terminated early if the resulting rest satisfied the minimum regulatory requirements. ALPA asked whether an air carrier could contact a flightcrew member when the flightcrew member is off duty but not on a rest period to give a flight assignment. If so, ALPA questioned whether the carrier must provide at least 10 hours of rest prior to the flight assignment. ALPA also asked whether a flightcrew member could voluntarily elect to “pick up a trip” from open time if he or she will have the requisite rest prior to the report time for that trip.

As discussed above, the start of a previously-scheduled FDP can only be changed by utilizing the reserve provisions of § 117.21. As such, a certificate holder that wishes to bump up the time of a previously-scheduled FDP would have to provide the flightcrew member with the pertinent long-call-reserve notice of the FDP change. Alternatively, if a certificate holder anticipates that it may need to call in a flightcrew member for an FDP, then that certificate holder should provide the flightcrew member with the required 10-hour rest period and then place the flightcrew member on short-call reserve.

These circumstances change if a flightcrew member decides, on his/her own initiative, to pick up a trip from open time, as the regulations do not prohibit this practice as long as the flightcrew member has received the required rest. However, the FAA cautions flightcrew members that § 117.5(a) requires a flightcrew member to “report for any flight duty period rested and prepared to perform his or her assigned duties.” The preamble to the final rule explains that this provision was added to the regulations to, among other things, “discourage flightcrew-member practices such as picking up extra hours.” [44] Thus, while a flightcrew member is free to voluntarily pick up extra flight hours from open time, the flightcrew member may be in violation of § 117.5(a) if this activity results in the flightcrew member becoming unduly fatigued.

Turning to ALPA's other question, if a flightcrew member is not on a rest period, the certificate holder may contact the flightcrew member to schedule a flight assignment. [45] However, pursuant to § 117.25(b) and (e), the certificate holder would then need to provide that flightcrew member with the requisite rest period prior to beginning the FDP. The certificate holder would also have to follow the FDP notification requirements of long-call reserve, as this type of contact and FDP assignment would qualify as long-call reserve pursuant to the definition of that term in § 117.3.