My wife carried her wedding dresss in the wedding dress coffin (it's just a big white box they charge triple for) over to Scotland for ours. I did have to ask other passengers to kindly not place things on top of it, but people were quite understanding and willing to accomodate. The box fit in the overhead bins on the 757 we were on no problem. It didn't crush or anything so that was fine. You need the wedding dress coffin afterwards if your wife is keeping the dress anyway.

That wasn't on Air Canada though; hopefully they'd be as accomodating.

Congratulations on your forthcoming nuptuals.