page_title: Four-engined jet aircraft
section_title: Later decades and gradual decline
hierarchical_section_title: Four-engined jet aircraft / History / Later decades and gradual decline
caption_attribution_description: Español: Boeing 777-31H/ER Emirates A6-EGK, Madrid, España.English: Boeing 777-31H/ER Emirates A6-EGK, Madrid, Spain.
context_page_description: A four-engined jet, sometimes called a quadjet, is a jet aircraft powered by four engines. The presence of four engines offers increased power, allowing such aircraft to be used as airliners, freighters, and military aircraft. Many of the first purpose-built jet airliners had four engines, among which stands the De Havilland Comet, the world's first commercial jetliner. In the decades following their introduction, their use has gradually declined due to a variety of factors, including the approval of twin-engine jets to fly further from diversion airports and an increased emphasis on fuel efficiency.
context_section_description: By the 1960s it became apparent that having four engines reduced fuel efficiency. This was not an issue for long-haul routes which carried 300 or more passengers for 8 to 12 hours, allowing for a high cost-to-passenger-mile ratio. On the other hand, the large four-engined types were less suited for frequent short-haul services, which demanded multiple take-offs and landings daily, costing more fuel while also typically carrying fewer passengers per flight. This prompted the development of large trijets and twinjets. Due to limitations in engine technology, twinjets of this era were small and had relatively short range. The FAA's 60-Minute Rule also prevented them from flying further than 60 minutes away from diversion airports due to their lower engine redundancy. Trijets represented a compromise between fuel efficiency and redundancy. In 1969, Boeing launched the 747. Nicknamed the "Jumbo Jet", it was the first wide-body airliner, able to carry significantly more passengers than any other aircraft. Its capacity and performance were unmatched, even after the launch of wide-body trijet competition in the form of the McDonnell Douglas DC-10 and Lockheed L-1011 TriStar.
  Within its own category in commercial aviation, the supersonic airliner Concorde began service in 1976. Its four Rolls Royce/Snecma Olympus 593 turbojets allowed it to cruise at twice the speed of sound. At the time of inception it was regarded as the future of air transportation. However, in large part due to high operating costs and noise issues, Concorde never achieved the predicted level of success.
  In the 1980s, the increased reliability and available power of jet engines enabled twinjets to safely fly on one engine. This prompted the introduction of ETOPS ratings for twinjets, allowing them to circumvent the 60-Minute Rule and fly on transoceanic routes previously serviced by four-engined types. The advantage of redundancy brought by four engines was no longer necessary and they could no longer compete with the lower fuel consumption and maintenance costs of twinjets with higher-powered engines. All but the largest four-engined types, such as the Boeing 747, became uneconomical and this led to the retirement of the ageing 707 and DC-8 fleets.
  A new wave of even higher-capacity four-engined designs arrived when Boeing launched the 747-400 in 1989 and Airbus launched its A340 in 1993. Both had high capacities (over 300 passengers) and long range, a combination still unmatched by twins at the time, and so were commercially successful.
  When the BAe 146 was introduced in 1983, it was unusual because it was a four-engined short range regional airliner. Its design ultimately enabled quieter operation and short take off and landing capabilities.
  The final major advantage of four engines, their potential for very large capacities, became much less significant when the twin-engined Boeing 777 was introduced in 1995. The original 777-200 could seat upwards of 300 passengers, a significant increase upon existing twinjets such as the 767, which could typically only seat 200-300 passengers. The subsequent development of the 777-300ER pushed the passenger capacity to just under 400, approaching the 747 and superseding the A340, while being more efficient and incurring lower engine maintenance costs. The Airbus A330 twin underwent a similar evolution, culminating with the 330-seat A330-300.
  By the early 2000s, the only remaining advantage of the largest types was their ability to carry more passengers than the largest twinjets. In the years following the September 11 attacks, the increase in fuel prices and decline in the aviation industry heightened the need to minimise operating costs and expenditures. Production of the 747-400 passenger variant ceased by 2005 and deliveries of the A340 dropped to 11 per year, as they faced competition from more efficient and comparably capable twinjets.
caption: Large twins such as this Boeing 777-300ER can almost match the capacity of the largest four-engined types.
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