My personal experience - and as posted elsewhere here on FT/DL - is that DL says if they can't substitute a schedule within 90 minutes of your original departure or arrival time, they'll give you a refund. I had 2 tix to SJU and there just wasn't anything within 90 min, so, I got a VERY prompt refund! I don't think they'll do it at 60 min., but you can always try! - AND, do the standard FT procedure . . . If you don't get the answer you want, just hang up and call back!!