Blimps are aircrafts that appear in Grand Theft Auto: Vice City and in Grand Theft Auto V.
In GTA Vice City, they are unobtainable because it is rather impossible to be reached with any air vehicle. It is usable in GTA V if the player pre-ordered the game, also it can be usable if the player calls the Blimp from the player's cellphone or flying a helicopter on top of the Blimp and entering it from there. As seen here