http://www.yapta.com/enter/
Planning a trip? Use Yapta to track prices before you buy!
The average ticket price fluctuates by 400%. Get Yapta and buy when prices drop.Already purchased a ticket? You may qualify for vouchers or refunds!
Guaranteed Airfare Rules entitle you to rebook if a lower fare is available - you get the difference as a credit for future travel. Simply add your ticket information. Yapta will email you if the price drops below what you paid, making you eligible for a voucher or refund from the airline.