Rolls-Royce RB211 is a three-spool turbofan family launched for the Lockheed L-1011 TriStar and developed through RB211-22B, RB211-524, and RB211-535 branches. The family powers Boeing 747 and 767 widebody variants and Boeing 757 aircraft, with the RB211-535E4 remaining a supported 757 powerplant; its architecture also supplied the lineage and technology foundation for later Trent engines.