The only EDF Aircrafts I ever saw on the ground were in the Badlands Aircraft Storage facility. But since the mission stated you had to destroy them, it wouldn't let you drive them. Other than that I have NEVER seen any aircrafts on the ground. I've tried getting a headshot with the Railgun on the pilots when they were close enough to the ground that the fall wouldn't destroy the aircraft, but it always seems to blow up when the pilot dies.
It's very frustrating.