To be honest, I don't know, and probably shouldn't have just assumed that. I know WN will and AS will, but don't really know about other airlines policies. My return VX flight was uneventful, so I didn't have any opportunity to inquire. The one pitfall I did encounter is that on VX, your ticket is worthless if you miss the flight, because unfortunately that's exactly what happened on my first VX experience, and only by a matter of minutes. I ended up redeeming a one-way WN award to get to my destination.