Hawker Siddeley Trident 1978, 117 Tridents had been produced. BEA's successor British Airways withdrew its Tridents by the mid-1980s. Trident services ended in China in the early 1990s. In 1953, as British European Airways (BEA) introduced the world's first turboprop-powered civil airliner – the Vickers Viscount – into passenger service, the operator was already considering what would be required of a potential successor. Following the entry into service of jet airliners in 1952, many airline managers and economists remained sceptical and advocated turboprop airliners as replacements of piston-engined airliners. In 1953, while several manufacturers across the world were investing in pure jet-powered aircraft,
Turboprop Kaman's K-125 synchropter, which used a Boeing T50 turboshaft engine to power it on 11 December 1951. Compared to turbofans, turboprops are most efficient at flight speeds below 725 km/h (450 mph; 390 knots) because the jet velocity of the propeller (and exhaust) is relatively low. Modern turboprop airliners operate at nearly the same speed as small regional jet airliners but burn two-thirds of the fuel per passenger. However, compared to a turbojet (which can fly at high altitude for enhanced speed and fuel efficiency) a propeller aircraft has a lower ceiling. The most common application of turboprop engines in