The Rolls-Royce RB211 is a family of high-bypass turbofan

Turbofan

The turbofan is a type of airbreathing jet engine that is widely used for aircraft propulsion. A turbofan combines two types of engines, the turbo portion which is a conventional gas turbine engine, and the fan, a propeller-like ducted fan...

 engines made by Rolls-Royce plc

Rolls-Royce plc

Rolls-Royce Group plc is a global power systems company headquartered in the City of Westminster, London, United Kingdom. It is the world’s second-largest maker of aircraft engines , and also has major businesses in the marine propulsion and energy sectors. Through its defence-related activities...

 and capable of generating 37,400 to 60,600 pounds-force

Pound-force

The pound force is a unit of force in some systems of measurement including English engineering units and British gravitational units.- Definitions :...

 (166 to 270 kilonewtons) thrust

Thrust

Thrust is a reaction force described quantitatively by Newton's second and third laws. When a system expels or accelerates mass in one direction the accelerated mass will cause a force of equal magnitude but opposite direction on that system....

. Originally developed for the Lockheed L-1011

Lockheed L-1011

The Lockheed L-1011 TriStar, commonly referred to as the L-1011 or TriStar, is a medium-to-long range, widebody passenger trijet airliner. It was the third widebody airliner to enter commercial operations, following the Boeing 747 and the McDonnell Douglas DC-10. Between 1968 and 1984, Lockheed...

 (TriStar), it entered service in 1972 and was the only engine to power this aircraft type. Although the costs of development forced Rolls-Royce Limited

Rolls-Royce Limited

Rolls-Royce Limited was a renowned British car and, from 1914 on, aero-engine manufacturing company founded by Charles Stewart Rolls and Henry Royce on 15 March 1906 as the result of a partnership formed in 1904....

 into bankruptcy and nationalisation by the British government, the company survived and the RB211 became the first true three-spool engine, which also turned Rolls-Royce from a small player in the airline industry into a global competitor.

The RB211 was officially superseded in the 1990s by the Rolls-Royce Trent

Rolls-Royce Trent

Rolls-Royce Trent is the name given to a family of high bypass turbofan aircraft engines manufactured by Rolls-Royce plc. All are developments of the RB211 with thrust ratings of . Versions of the Trent are in service on the Airbus A330, A340, A380, Boeing 777, and 787, and variants are in...

 family of engines, the conceptual offspring of the RB211.
In 1966 American Airlines

American Airlines

American Airlines, Inc. is the world's fourth-largest airline in passenger miles transported and operating revenues. American Airlines is a subsidiary of the AMR Corporation and is headquartered in Fort Worth, Texas adjacent to its largest hub at Dallas/Fort Worth International Airport...

 announced a requirement for a new short-medium range airliner with a focus on low-cost per-seat operations.