Concorde
Actually Concorde was quite profitable, at least for British Airways if not for Air France. (There was an agreement that both would continue flying them until both mutually agreed not to.) There was a big enough market willing to pay the premium for the time saving of crossing NYC (or earlier Washington) to London for them to always run at capacity. There were some people who did day trips to London and back! An expensive way to avoid jet lag...
In fact after the accident when BA finally acceded to Air France's desire to stop flying them, Richard Branson wanted to take over BA's Concorde fleet and run them under the Virgin flag.
