Whitley test "produced a failure at 98% of the design load" is that good?

[Bill Walker]

The wing skins could have been a classic "zipper" failure. I'm assuming the Whitley wing skins were metal panels riveted on. If a few rivets fail (or are shot away) the panel load re-distributes over the remaing rivets. At some point this re-distributed load will exceed the breaking strength of a rivet, this one pops, the load re-distributes and the next one pops, and so on until the entire panel can fall free. Like undoing a zipper. If a corner or edge of the panel lifts and gets high speed air under the panel, the effect can be quite quick.

There have been cases where one panel tearing off damages rivets at an overlapping seam, and the next panel proceeds to unzip as well.