Why did Air France retire Concorde?
Ultimately the cost of flying the aircraft was more than the revenue that it generated.  The Concorde began a steady decline to retirement after the firey crash of Air France Flight 4590 which killed 113 people, and again suffered setback after September 11th, 2001.  Even with the best safety record in airline history, the crash combined with the terrorist attacks led to passenger fear and low sales. Airlines that operated the Concorde eventually lost money on most flights, and long term operations were simply not sustainable.  To make matters worse, it was very limited to which airports it could fly to in the US: JFK, IAD and DFW. The FAA was opposed to the Concorde for pollution, noise and fuel inefficiency concerns.

British Airways cites mostly political reasons for the ending of its Concorde program.  They claim that the Concorde would have remained profitable had Airbus retained the airplane.  However, there was also speculation that, due to the dwindling numbers of passengers, BA realized that it could make more money carrying passengers subsonically across the Atlantic.