Many people have a huge investment in their frequent flier programs, having spent years accumulating miles for a long-awaited trip. But with Delta Air Lines (NYSE:DAL) changing its frequent-flier program rules, many fear that their miles might be at risk and that they won't get the full benefits they're used to receiving in the future.

In the following video, Dan Caplinger, The Motley Fool's director of investment planning, goes through the changes to Delta's frequent-flier program and the potential impact on United Continental (NASDAQ:UAL) and American Airlines Group (NASDAQ:AAL). Dan notes that Southwest (NYSE:LUV) made similar changes to its program, emphasizing the amount you pay for a ticket rather than the number of trips or the distance you travel. As airlines work to be more profitable, they want to reward the customers that are most important for their success, and that means rewarding business travelers even more than traditional airline-mile programs did. Dan concludes that if Delta's program is a success, then you can expect United and American to follow suit soon.