The Cotton Flight suits were standard issue in 1967 when I began Army Flight School....ours were the gray version, there Orange flight suits seen but were usually worn by the Flat Iron detachments (think Army style SAR/Medevac crews stationed at the large training bases flying CH-34's then later UH-1D's.
The Air Force, Navy, and Coast Guard wore the Orange suits more often than did the Army.
In the latter part of 1968 and early 1969 we began to see the introduction of the Nomex Two Piece flight suit for Army Crews in Vietnam.
The Army has struggled over what style....two piece or one piece...drab or camouflage....as they struggle on most commonsense issues.
The non-aviation infantry Generals have a love-hate thing with Aviators.....just as they do with Spec Ops types who do not always dress as does the straight leg orthodox infantry.
I see as being a magnum case of Penis Envy....simple example is the entire Army wearing Black Berets....when the Black Beret was earned and worn by Rangrers.
When the Special Forces guys began to wear the Green Beret in the early 1960's.....it took President Kennedy to get involved to get the Army Dinosauers to wind their necks in.
So be it head gear, boots (remember the early paratrooper and their High Top Jump Boots), or flight suits.....the peevish always object to anything different than what they must wear in the US Army.