The BAC One-Eleven is an early jet airliner produced by the British Aircraft Corporation (BAC). Originally conceived by Hunting Aircraft as a 30-seat jet, before its merger into BAC in 1960, it was launched as an 80-seat airliner with a British United Airways (BUA) order on 9 May 1961. The prototype conducted its maiden flight on 20 August 1963, and it was first delivered to BUA on 22 January 1965. The 119-seat, stretched 500 series was introduced in 1967. Total production amounted to 244 until 1982 in the United Kingdom and between 1982 and 1989 in Romania where nine Rombac One-Elevens were licence-built by Romaero.

A narrow-body aircraft or single-aisle aircraft is an airliner arranged along a single aisle, permitting up to 6-abreast seating in a cabin less than 4 metres (13 ft) in width. In contrast, a wide-body aircraft is a larger airliner usually configured with multiple aisles and a fuselage diameter of more than 5 metres (16 ft), allowing at least seven-abreast seating and often more travel classes.