Under which condition can an IFR flight plan be filed inflight?

• A. In uncontrolled airspace waiting to enter IFR in controlled airspace
• B. In controlled airspace after entering IFR
• C. Only on the ground before departure
• D. Not allowed to file inflight

Answer: (A)

Filing an IFR flight plan while airborne is allowed when you’re in uncontrolled airspace and you’re waiting to enter IFR in controlled airspace. In that situation there’s no active ATC clearance to enter the controlled area yet, so you can contact Flight Service or ATC to file or amend your IFR plan and obtain the necessary clearance before you enter the IFR segment. This lets you switch to IFR midflight without returning to the ground. It isn’t about filing only on the ground, and inflight filing isn’t disallowed; the described condition—being in uncontrolled airspace en route to IFR in controlled airspace—is the valid scenario for inflight filing.