14 CFR §117.11

1. (a)No certificate holder may schedule and no flightcrew member may accept an assignment or continue an assigned flight duty period if the total flight time:
   1. (1)Will exceed the limits specified in Table A of this part if the operation is conducted with the minimum required flightcrew.
   2. (2)Will exceed 13 hours if the operation is conducted with a 3-pilot flightcrew.
   3. (3)Will exceed 17 hours if the operation is conducted with a 4-pilot flightcrew.
2. (b)If unforeseen operational circumstances arise after takeoff that are beyond the certificate holder's control, a flightcrew member may exceed the maximum flight time specified in paragraph (a) of this section and the cumulative flight time limits in 117.23(b) to the extent necessary to safely land the aircraft at the next destination airport or alternate, as appropriate.
3. (c)Each certificate holder must report to the Administrator within 10 days any flight time that exceeded the maximum flight time limits permitted by this section or § 117.23(b). The report must contain a description of the extended flight time limitation and the circumstances surrounding the need for the extension.