Thanks, chaps - I've learned a lot ! All through my "career" (?), flying instructors were addressed as "sir", no matter what the disparity in rank.
I myself went from Sergeant Pilot to Pilot Officer painlessly (without benefit of OCTU) - see my Post:"Danny has Greatness Thrust upon Him" ("Pilot's Brevet" Thread, Page 131, #2612). Excerpt:
..."Up to then, I'd been quite content to remain an NCO. I'd been a bit disappointed when I got my wings without even having been considered for a commission. But I'd settled down and, had I stayed in the UK, would have hoped, had I lived (more than doubtful), to rise to Flight Sergeant * (one year) and Warrant Officer (two years) on time promotion. But this latest business seemed most unfair.
[Note *: My crown was two weeks overdue - never did get the money !
]
I went to see the C.O. "Why not ?" he said wearily, "Everybody else is getting it - I'll put you up" (my misdemeanour at Dum-Dum seemed to have been forgiven). It was a formality from then on. I was called for interview with the AOC of 221 Group in Calcutta, a kindly old AVM (Williams, I think), He satisfied himself that I didn't drop my aitches, and could probably use a knife and fork, and signed me in. Thus are careers made........OCTU ?........ What's that ?"...
Danny.