The LA Times pulls back the veil  on what must be one of the worst in a series of bad business choices made by American Airlines. In 1981, it wanted to borrow millions to expand its operations, but was stymied by record-high interest rates. Rather than borrowing on the books, the company looked for alternative ways to raise the moeny, and decided to launch the AAirpass:
It was, and still is, offered in a variety of formats, including prepaid blocks of miles. But the marquee item was the lifetime unlimited AAirpass, which started at $250,000. Pass holders earned frequent flier miles on every trip and got lifetime memberships to the Admirals Club, American's VIP lounges. For an extra $150,000, they could buy a companion pass. Older fliers got discounts based on their age.
The company thought that the biggest customers would be businesses buying the passes for top executives. What they didn't count on was the change in behaviour that being able to take a $125,000 trip to London for free would spark:
[Steven Rothstein] was airborne almost every other day. If a friend mentioned a new exhibit at the Louvre, Rothstein thought nothing of jetting from his Chicago home to San Francisco to pick her up and then fly to Paris together.
In July 2004, for example, Rothstein flew 18 times, visiting Nova Scotia, New York, Miami, London, Los Angeles, Maine, Denver and Fort Lauderdale, Fla., some of them several times over. The complexity of such itineraries would stump most travelers; happily for AAirpass holders, American provided elite agents able to solve the toughest booking puzzles.
In 2007, the airline finally realised that the people they had sold unlimited passes to – which peaked at a price of $1.01m before being discontinued in 1994 – were costing them upwards of $1m every year. So they started to crack down. 
It seems like there should be a moral to this story, but I'm not sure what it is. Perhaps that if you set marginal prices below marginal costs, someone is going to take advantage of that. Perhaps that if you want to borrow some money, just get a loan from a bank like everyone else. Or perhaps, given American have started stripping passholders of their perks, that the house always wins.