In Cornell's presentations, they show some carefully-selected frames that appear to show white on the bird's back, but I'm completely unconvinced that this white was present on the actual bird. I say that for two reasons:
One interesting thing was the total lack of emotion or movement from the Luneaus in the boat when the bird flies by. If I had thought I'd just seen an IBWO, I'd be jumping up and down and probably end up in the water. One detail that is much clearer on the blown-up video is the white on the bird's back, which I could never clearly see on the computer or even on television.
1. I've studied the Luneau DVD frame-by-frame, and I see plenty of frames where the back looks entirely black.
2. If you watch the trees in the Luneau DVD, you can also see apparent white smudges on them that appear and then disappear.