14 C.F.R. § 91.173 ATC clearance and flight plan required.
Title 14 - Aeronautics and Space
No person may operate an aircraft in controlled airspace under IFR unless that person has— (a) Filed an IFR flight plan; and (b) Received an appropriate ATC clearance.
Title 14: Aeronautics and Space
PART 91—GENERAL OPERATING AND FLIGHT RULES
Subpart B—Flight Rules
Instrument Flight Rules
§ 91.173 ATC clearance and flight plan required.
