Refuelling a $100m, American F-35A fighter jet at 350mph
F-35A fighter jets from America are currently flying out of RAF Lakenheath, in Suffolk, on their first overseas training exercise.
By 2021 they will be permanently based there and at RAF Marham in Norfolk.
BBC News took a trip on a KC-135 Stratotanker as it refuelled two F-35As during a flight to Bulgaria.