Wrong. All you have to do is click the "show object id" button, and find the ID of the building. Then put "deletevehicle object XXX" in an init field somewhere, and VIOLA! No more building! You can also move buildings around this way, if I'm not mistaken, using the setpos command.
But no, you can't add runways; they are terrain tiles (like grass or sand), and not objects (like roads).