Back when I started airline flying, 1969, the big "concern" was "high altitude stall".
I recall captains taking airplanes well above a safe flight level.
As an example, overflying towering CBs in the USA Midwest...
I recall being at FL410 in a B-720 where chart maximum was FL370/380.
This captain "ace" got us 2 or 3 times in a stick shaker... Was about Mach .82.
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As a flight engineer and first officer (727) some captains extended T/E flaps disabling leading edge devices.
The VFE speed limit on 727 (and 747) is directly related to leading edge VFE structural limit.
The "T/E Flaps 1 position" (747) or "T/E Flaps 2 position" (727) is not a VFE speed limit.
For these position, the trailing edge flaps extend the surface of the wing, not any drag increase.
But the VFE related to these positions is related to L/E flaps structure.
It is a certification limit. Maximum altitude for flaps 707-727-747 = 20,000 ft.
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With the DC8-60/70 - there was a VFE and MFE limit.
Flaps 12 was 230 KIAS VFE or .46 Mach. OK to extend above FL 200.
Stall recovery procedure DC8...? Extend first notch of flaps, any level. Approved UAL procedure.
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So - try to figure what "Hoot" Gibson did... I suspect he did...
Just was not an approved procedure. Never has been, but some did...
He probably wanted to be higher to avoid CAT, than flying 100 NM off his track...
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The bulk erase...? Yes - in the "old days" I always did use that feature...
The last 15 years of my career, I no longer used that feature.
Every pilots bust at least "one limitation" (or regulation) per flight.
You never do...? - Shall I call you a liar...?
And now retired, I could not care less...
xxx
Happy contrails