When I joined in 1975 it was min 5 O levels for officer aircrew and 3 O levels for NCO air eng, loadmaster etc. However at seventeen and a half, with 6 O Levels, I enquired about NCO air eng but was "persuaded" by the CIO to go for propulsion tech with a view to remustering to air eng later on. It was probably the right decision as I wasn't mature enough as a 17.5 year old and I'm sure I would have flunked the course.