Lord Lucien
Lets all love Lain
2Lts and Lts typically only stay those ranks for a few years each. Once they hit Captain, most officers tend to stay that rank for a long time. It's the first officer rank of any real worth, and it showcases a minimum time in.
I'm not 100% on how the USAF works, but I know the RCAF requires every pilot to be an officer. The USAF has quite a few aircraft so that might account for a bit of the bloated officer numbers. Most other Air Force NCMs likely being aircrew or technical crew. It's just not the same environment or requirement as an Army platoon of NCMs led by a single officer.