Dansyr -- US Air will give you a transportation voucher for the amount it has dropped. Now you must book within 1 year of getting the voucher and you can book 1 year ahead. So in theory you could fly 2 years from voucher. Now the deal is, your flight has to still be availabe ( I think) for purchase, not sold out. And you cannot book online.
I have $100 in vouchers I need to use before Aug, but I couldn't use them against the great online rate I just got for Feb 2005.
I will need to book something by Aug 23.
USAir used to just credit you credit card, oh they were the days.