The U.S. Mint has closed a loophole that allowed owners of credit cards with airline miles to rack up free fares— without spending any money. Credit card users across the country are smacking their heads and asking themselves why they didn’t think of that earlier. In an effort to spread $1 coins into circulation, the U.S. Mint had been offering what it thought was a zero-sum deal to consumers: the ability for citizens to purchase large quantities of $1 coins at face value. In other words, you charge $5,000 on your credit card, and a few days later $5,000-worth of $1 coins would arrive on your doorstep.