During the Cold War era, numerous innovations were introduced to the flight deck. The angled flight deck, invented by Dennis Cambell of the Royal Navy, was one prominent design feature that drastically simplified aircraft recovery and deck movements, enabling landing and launching operations to be performed simultaneously rather than interchangeably; it also better handled the higher landing speeds of jet-powered aircraft. In 1952, became the first aircraft carrier to trial the angled flight deck. Another advance was the ski-jump, which fitted an angled ramp on the flight deck near the end of the aircraft's takeoff run; the change greatly reduced the distance required and became particularly useful for operating STOVL aircraft. Furthermore, various unsuccessful concepts to replace or compliment the conventional flight deck have emerged over the years, from the flexible flight deck to the submarine aircraft carrier and flying boat fighter aircraft.