User blog comment:Trevor Philips/GTA V Questions/@comment-4210063-20130922185746/@comment-4210063-20130922194450

Planes will spawn at Sandy Shores Hangar (Trevor) and Los Santos International Airport Hangar (Michael or Franklin).

Tank and military trucks will spawn at LSIA Hangar (not sure about the SS one).

Military Helicopters will spawn at the Sandy Shores Helipad (Trevor), not sure about others.

Small military vehicles like Mesa will (should) spawn at Grove Street (Franklin), Vinewood (Michael) and Pilbox Hill (Trevor) garages.