sentences: "The flight of the "Question Mark" did spark an interest in aerial refueling by the Royal Air Force, seeking to minimize takeoff weights of its bombers and reduce wear-and-tear on its grass airfields, but after a series of experiments between 1930 and 1937 they abandoned testing.The development of better engines, variable-pitch propellers and all-metal low-wing monoplanes capable of greater range deferred further military interest in aerial refueling, but when the next war turned out to be global in scale, also resulted in lack of capability for many ferrying, antisubmarine, and bombardment operations requiring extended range.