I just got back from Tulum Mexico flying with sunwing and I was quite impressed. I thought I would post about it because someone was asking about experience with them a while ago and I couldn't find that post again. I was a little worried at first because I was over their weight limit of 20kg (my gear was 25kg), but they didn't give me any hasstle or charge me anything extra. I didn't even call ahead and register it or anything and I told them that it was a kiteboard. Although the attendant in Cancun didn't speak english and it ended coming back as SCUBA gear.
It would be good to know of the airlines that should be avoided for kiteboarding trips.