People in the US got free flights by buying money from the government. People would buy 1$ coins in bulk from the US mint (free shipping) and pay off their credit card bill with the coins. They would buy the coins with credit cards that awarded frequent flyer miles, thus getting them free miles.
How Frequent Fliers Exploit A Government Program To Get Free Trips We recently reported on the the government’s failed effort to persuade Americans to use dollar coins. But the coins have found at least one group of fans: Travel enthusiasts who buy thousands of dollar coins with credit cards that award frequent-flier miles for purchases. […]