Credits and refunds

[jstbcuz]

Can someone tell me which airlines gives you credits or refunds if you find a cheaper flight?

I know SW gives you credit to use within a year and doesnt charge, but what about other airlines? I am specifically looking for those that dont charge a fee for this.

THanks!

 

[tinknme]

Airtran will give you a credit that has to be used within a year.