A "Flight School" update for Grand Theft Auto 5 is coming out tomorrow, August 19th. The video on Rockstar's website seems to indicate that military jets, which were previously only available on a temporary basis by stealing them from the military, may be up for sale. Along with new helicopters and cars. The video also indicates that parachutes with designs to match the flags of several countries will be available.
More information along with the video can be found on Rockstar's Blog