Your mission is to attack the airfield and destroy the enemy jets before they can launch ...
Or, the model sits to the side of the table or on a stand over it to indicate that you have air assets deployed, rather than to show the actual position of an individual aircraft.
There was a quite brilliant model "asset marker" type doing the rounds of the UK shows some years back in a WW2 game. It was a Typhoon destroying a German tank. The trick was that the (weighted) model exploding Panzer acted as a base - metal rods running from it inside the modelled rocket trails held up the aeroplane, so it looked like it was suspended in mid-air.