I think you have to open them up manually by clicking on the 'plates' tab and clicking on the yellow plane symbol. I guess if it did it automatically other people would complain it was distracting everytime they flew over an airfield. I must admit if the airport was a destination airport, as opposed to en-route, then it should open up automatically, but I havent found a way to make it do that. Still, its a brilliant product in all other respects.