|Values:||Boolean values: yes or no, true or false, 1 or 0|
Set Selectable=no to an object that should not be selected by the player.
Usually this is combined with uncontrollable objects and/or spawns, to prevent the player from selecting objects that they should not have control over. Examples include the V3 Rockets and Dreadnought Missiles (the actual missiles, not their launcher units).
Adding Selectable=no to spawned AircraftTypes with aircraft Locomotor randomly causes them to fly over the map border instead of landing, and thus crashing the game. If that AircraftType has to land on it's spawner for reloads, sometimes it just starts hovering over the VehicleType and never fully lands. You'll have to move it first. With luck, you'll need to do that only once ot twice.