As a humble turboprop pilot I rarely venture into these lofty realms - however, many moons ago as a F/O on a venerable Convair 580 turboprop freighter operating downunder, I had the misfortune to experience a complete failure of the pitot static system on takeoff at night into a low overcast and driving rain.
The usual pitch attitude did not (apparently) give the expected performance, so I reduced the pitch angle from (the usual) 7deg nose up to 5 deg. Speed and ROC continued to (apparently) decrease. I was about to reduce the pitch further when (mental) alarm bells started ringing. I was well below 1000 a.g.l at night, both engines were running and yet the instruments wanted me to pitch forward.
I announced to the Captain that there was a serious issue with the pitot-static instruments and I was reverting to power and attitude only. Won't bore you with the rest of the details; I will only say that the urge to pitch forward to "regain airspeed" was almost overpowering. Watching the ASI decrease towards (and eventually below) stall speed was terrifying, knowing that I was betting our lives on my assessment. The ol 580 didn't have checklists for these situations.
All ended well but it remains the single most terrifying few minutes (and also my proudest) of my career to date.
I can only imagine what this crew was thinking and trying to understand and my heart goes out to them, having some tiny inkling of the confusion they must have felt.