We canceled a flight just before Christmas in 2007. I am booking an international trip in September and would like to purchase tickets soon. I would like to use the credits from the canceled flight. I cannot figure out how to do that online. Do I have to call DL and make telephone reservations in order to use that credit?

I have never done this before, but I think that I will not receive full credit for the canceled flight. How much will DL keep of the original amount we paid?