I was able to redeposit my original US Air award. From the time I booked the award until last week, two or three schedule changes caused my LGA-PHL connections to extend from 2 hours to just over 4 hours. Also, the return flight went from a mainline jet to an express flight, so I lost my F seats. Because of these changes, I was able to cancel (redeposit) the award for no fee.

They do not accept the new cities as a reason to redeposit existing awards without a fee.