If you are on board a military aircraft are you not in effect then on sovereign territory
No.
The point was tested. Few years back when an Israeli general was onboard an aircraft at Heathrow and the plods were waiting to arrest him when he disembarked. The crew got word and he remained on board, the plods stayed outside and he went home on the return flight.
The judge who issued the warrant subsequently then ripped several new arseholes in the plods for their failure to board and arrest.
Keeping the peace? The El Al flight and the Israeli army officer | The Independent