How to have random harriers take off from base?

[magicalflump 1]

Hi, on my mission, the base if full of everything that everybody needs, planes, choppers, armor ect. However to make the base more life-like and realistic ive added AI soldiers walking around the base, and at the start there are some harriers that take off from base and just go out of the map.

What i want to know is, is there a way to have some harriers that take off, go into the distance, despawn, then respawn back at base in 20-30 minutes then take off again?

Thanks

[[frl]myke 14]

This belongs to mission editing..moving.