Improperly-rigged heavy drops.

I used to be in a unit that did these. Heavy drops always go first for just this reason. Paratroopers follow. One can see why the opposite might be a problem.

My unit used to drop tanks from the air. This is no longer done, but wow was that a sight to see. They were M551 Sheridan light tanks — “light” in this case still means they weighed 34,000 pounds each.

Below is a pretty decent video of what I used to do for a living. I’ve jumped out of both those aircraft types onto that specific drop zone many times.