14 C.F.R. § 135.217 IFR: Takeoff limitations.
Title 14 - Aeronautics and Space
No person may takeoff an aircraft under IFR from an airport where weather conditions are at or above takeoff minimums but are below authorized IFR landing minimums unless there is an alternate airport within 1 hour's flying time (at normal cruising speed, in still air) of the airport of departure.
Title 14: Aeronautics and Space
PART 135—OPERATING REQUIREMENTS: COMMUTER AND ON DEMAND OPERATIONS AND RULES GOVERNING PERSONS ON BOARD SUCH AIRCRAFT
Subpart D—VFR/IFR Operating Limitations and Weather Requirements
§ 135.217 IFR: Takeoff limitations.
