[article] It happened to Louise Andrew twice last month. She made reservations on the United Airlines website, tried to cancel them within 24 hours for a full refund, and was told that the airline would be happy to issue a ticket credit instead. “Both times, I was initially told that my purchase value would be applied to a future ticket,” says Andrew, an attorney from Redmond, Wash. That didn’t make sense to her. United promises a no-questions-asked refund on most tickets, as long as the request is made within a day of the reservation. And since 2011, the Department of Transportation has required airline reservations to be cancelable without penalty for at least 24 hours after the booking is made, unless the ticket is purchased one week or less before a flight’s departure date. Andrew’s case illuminates the growing problem of ticket credit deflation. Historically, airlines have preferred to issue credit instead of a cash refund. They’re also fairly generous when it comes to parceling out vouchers for future flights. The reason? Redemption rates on vouchers hover somewhere between 5 percent and 8 percent, so there’s little cost to the company.