At Mission start the UAV flies circles over own Base. You have to walk to the UAV Terminal and use the UAV Option.
Then you can controll the Alttitude with the normal keys,you use in Chopper too.If you want the UAV to fly to a special
Position,you need to open the Map (when looking trough UAV),there you can order the UAV to fly somewhere else,But take care,
enemy Air Defense can shoot it down when flying too low altitude.Better fly high altitudes and zoom in (+- keys)