Traveling during the holiday season? Here's one way you can make sure you don't overpay on your airline ticket -- keep an eye on the price. Most airlines and online travel agencies will give you a rebate -- usually in travel credits or vouchers -- if your flight’s price drops below what you paid. Yapta.com will send you alerts if the price drops on a flight you've booked. Be aware, though, that some airlines can charge hefty fees for re-booking your flight. If the fee outweighs your rebate, it's not worth it to make a change.