Suppose you’ve paid for airline tickets, and then you find the same flight a week later for less cash. Is there anything you can do about it?

It turns out that there is. United, JetBlue, USAir, Southwest and Alaska will give you a voucher for the difference in price – if you know enough to ask them for it.

If you want to buy the new tickets, however, you may face serious fees – even for the same itinerary and on the same airline! Continental and America charge $100, Delta charges $50, Frontier charges $35 and Northwest charges $25.

Still, the difference in price might be worth it. If you’d like to be notified when your flight price is reduced, sign up for alert e-mails from yapta.com. You’ll have to act pretty much immediately when you get the alert, but it might be worth it.

(Thank you once again, Clark Howard)