In theory, I could go to a flight plan filing website, or even run AFPEX, over a satellite phone, and file a Eurocontrol flight plan while airborne. If one did this 500nm after departure, one might get some raised eyebrows, unless one lied and said one has just departed from an airport nearby (and one send a DEP message, possible with AFPEX, but that makes it an outright lie). I don’t...