So.. Just to see of this ideas OK. 

What if a new graduate of flight school,but was previously in the Raf as ground crew. Had good scores but wrong class. War comes. Air crew needed so they get trained. Had the scores to fly before but was not the right class or background for thr officer core, war time changed that and they just needed men. 

The trainees are sifted and was pulled for enlistment to new unit and assigned based on there test scored rather than class or background. 

There abit older. Say 30,s and had a few years in Raf as a ground mechanic or some other role?