The years between World War I and World War II saw great advancements in aircraft technology. World War II saw a great increase in the pace of development and production, not only of aircraft but also the associated flight-based weapon delivery systems. After World War II, commercial aviation grew rapidly, using mostly ex-military aircraft to transport people and cargo. This growth was accelerated by the glut of heavy and super-heavy bomber airframes like the B-29 and Lancaster that could be converted into commercial aircraft. The DC-3 also made for easier and longer commercial flights. The first commercial jet airliner to fly was the British de Havilland Comet. By 1952, the British state airline BOAC had introduced the Comet into scheduled service.