But as an instrument pilot, you have an option. You can “air file,” or file an IFR flight plan while en route. Ideally, this would involve calling up the nearest ATC frequency, stating your N number, and waiting for a controller to acknowledge your transmission.

Pilots can indeed file an Instrument Flight Rules (IFR) flight plan while already in the air, a process commonly known as "air filing." This is typically done by contacting a Flight Service Station (FSS) over the radio and dictating the flight plan details, which they then relay to Air Traffic Control (ATC). Alternatively, a pilot can request a "pop-up" IFR clearance directly from ATC if they are already in contact for flight following, though this is granted strictly on a workload-permitting basis. Air filing is often used when a pilot departing under Visual Flight Rules (VFR) encounters deteriorating weather conditions and needs the safety and structure of an IFR clearance to continue to their destination. However, the FAA generally discourages air filing for non-emergencies because it occupies valuable radio frequency time and increases controller workload. Modern technology, such as ForeFlight and Garmin Pilot, now allows many pilots to file via a tablet and cellular/satellite connection mid-flight, which is significantly more efficient than verbal dictation.