I looked all over the Airport but couldn't find it. Are there any prerequisites?
In my game, the AB Destroyer is parked in front of one of the hangars. If you look at the runway that goes east to west, north of this runway is a set of 5 buildings visible on your map.
The western building is the control tower, and there are 4 hangers to the east. The AB Destroyer was parked in front of the first hanger east of the control tower.
I'm not aware of any prerequisites, although in my game I do have 100% completion. The game is pretty liberal about giving out powerful vehicles, though. Normally, if there is an unlock condition, the vehicle will be given to you in a pack and immediately summonable via your phone.
You might have to destroy the Zinyak statue on top of the terminal (near the Snipes 57) to unlock it.