On any map, try Last Resort, first spawn a machine gun turret and have a person get on (need at least two people) it.

Then pick up the machine gun with the person on it and you can fly around holding the gun and the person still on the machine gun can keep shooting (so it's a aircraft)

And if the person holding the machine gun presses B, he will detach the gun, but after that if you look at the machine gun it will still be there!

So the trick can done again and again without spawning another one.