I had bought a restricted fare (non-refundable) ticket on Frontier Airlines last December. The flights were delayed during the Winter Storm, and Frontier agreed to cancel my itinerary, but not refund the fare for no service fee. They said that I should be able to use the funds for a future travel until a year from original purchase. I was wondering if I would be able to use these funds only on a Frontier Airlines ticket, or I could use it on Air Tran (mileage partner) ticket as well? The main reason for this is because I would like to fly to a city that is serviced by Air Tran, but not by Frontier Airlines.

TIA