I had one come loose once - by bumping it, not by highway wind. One of the metal arms that push-out and hold the glass in place came off the glass. It was just held on by some sort of glue. Didn't seem to take much of a bump to break the metal support off the glass. So to answer your question, "I'm not sure...," but we now keep our frameless windows closed while rolling down the road. We do keep the roof vents open, however. Hope that helps, \ken
Ken & Deb (WIT Club, FMCA, SKP, Harvest Hosts, and grateful volunteers with SOWERs)
2005 Winnebago Vectra 40FD w/400ISL and Allison 3000MH on Freightliner's Evolution chassis, Onan QD7500, 1000w Renogy solar, BlueOx tow gear, and 2015 Cherokee TrailHawk toad.