Many yrs ago when i joined the RAAF, One cadet aced ground school and then bombed out in the first stages of flying, taught us a lesson. 20 yrs later i did a stanine test in the US for World Airways , 4 guys failed, all Irish and they were all good operators. We all reckoned they failed on the low side and HR got rid of them. In the nineties i flew with a bloke who was a genius, IQ through the roof, failed every attempt at Command.