I ask the question because it seems like I saw someone do this. I was in a helicopter and picked a fight with someone on the ground (tried to drop a car on him). Within a few moments a fighter jet appeared over the garage he was hiding in. It proceeded to blow me out of the sky (no problem with that, I had it coming). We were nowhere near the military base.
Is there some way to keep a jet in a garage or order one up (i.e., from Merriweather or Lester). I looked and can't see any option like that.