Concorde was jointly developed and manufactured by Sud Aviation (later Aérospatiale) and the British Aircraft Corporation (BAC) under an Anglo-French treaty. Twenty aircraft were built, including six prototypes and development aircraft. Air France (AF) and British Airways (BA) were the only airlines to purchase and fly Concorde. The aircraft was used mainly by wealthy passengers who could afford to pay a high price in exchange for the aircraft's speed and luxury service. For example, in 1997, the round-trip ticket price from New York to London was $7,995 ($12.5 thousand in 2018 dollars), more than 30 times the cost of the cheapest option to fly this route.