§ 121.637 – Takeoffs from unlisted and alternate airports: Domestic and flag operations.
(a) No pilot may takeoff an airplane from an airport that is not listed in the operations specifications unless—
(1) The airport and related facilities are adequate for the operation of the airplane;
(2) He can comply with the applicable airplane operating limitations;
(3) The airplane has been dispatched according to dispatching rules applicable to operation from an approved airport; and
(4) The weather conditions at that airport are equal to or better than the following:
(i) Airports in the United States. The weather minimums for takeoff prescribed in part 97 of this chapter; or where minimums are not prescribed for the airport, 800-2, 900-1 1/2, or 1,000-1.
(ii) Airports outside the United States. The weather minimums for takeoff prescribed or approved by the government of the country in which the airport is located; or where minimums are not prescribed or approved for the airport, 800-2, 900-1 1/2, or 1,000-1.
(b) No pilot may take off from an alternate airport unless the weather conditions are at least equal to the minimums prescribed in the certificate holder's operations specifications for alternate airports.