I think this question was focused on aircraft. If I'm correct, does anyone have data for aircraft belts and latches specifically? On commercial aircraft I believe it is typically an Amsafe buckle. More here: http://www.amsafe.com/products-services/...ight-seatbelt/.

They're rated to 3000 lbs. Whether or not they jam at 3,000 lbs, I have no idea.