Sec. 91.173 - ATC clearance and flight plan required. 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.
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.