BAC One-Eleven suffered disasters in service, strong passenger demand had been demonstrated for jet propulsion. Several manufacturers raced to release passenger jets, including those aimed at the short-haul market, such as the Sud Aviation Caravelle. In July 1956, British European Airways published a paper calling for a "second generation" jet airliner to operate beside their existing turboprop designs. This led to a variety of designs from the British aerospace industry. Hunting Aircraft started design studies on a jet-powered replacement for the successful Vickers Viscount, developing the 30-seat Hunting 107. Around the same time, Vickers started a similar development of a 140-seat derivative
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