I'm having the same issue trying to apply travel funds that expire on 3/31/18. It will let me apply the other travel funds that expire later in the year, but obviously I want to use the earlier ones first. I realized today that the funds I'm trying to use are from a trip to Nassau - maybe that's the problem? I'll have to get my husband to call Southwest and see if we can sort it out, since it's his account and funds.