The B-2 stealth bomber is unique for a number of reasons. The first is that its flying-wing design makes it almost entirely invisible to radar. The second is that each B-2 has cost the American public an eye-watering $2.1bn making it the single most expensive aircraft in US military history.
Finally, it's that stealth bombers look cool no matter what they're doing.
This rare footage of a B-2 Spirit refuelling shows how the aircraft utilises a hidden port on the top of the aircraft that swivels round to reveal the fuel pump.
When it has finished, the port swivels back round and becomes invisible, blending into the surface of the bomber.
Giving the B-2 a refuelling capability was vital for its original purpose of being a Cold War bomber. Utilising this technique increased its range to a staggering 10,000 nautical miles.