Circling aircrafts

[WinterAssault]

I found some maps have their aircraft units circling well, is that trigger or something? Can someone teach me?

 

[Severalser]

Mmm, yes.. It's easy just set some point or region in the map and when the air unit enters to this point/region order it move to other point.

AirUnit -> P
^ ::::::::::::: |
| :::::::::::::: v
P <-------- P

It's a quare I know, just imagine