I sat the GAPAN tests in 1990 for the RAF, BA aptitudes in 2000 and GAPAN for myself in 2001. I passed all, but the differences...
The RAF set had a seperate set of navigation tests which involved lots of sums in a very short space of time, and a lot of time pressure reading from charts, but aside from that there wasn't much difference between that and GAPAN as paid for by Joe Public. The BA tests had some similar tests but also some interesting additions but all in all you could see they were all testing similar things, why would an airline pilot want to shoot down the enemy
But out of the crowd that I sat GAPAN with there were mostly Average High and Average scores (the scores being High, Average High, Average and Low).
From the several places where I've sat verbal reasoning and numerical reasoning, (pilot and engineering), they have all stated that there is no pass mark, though I'm sure a low mark would exclude you, but it gives them a good idea about you, are you an all rounder? or purely mathematical?.
But as Scroggs says I think it is more a tool to find who are not suitable rather than a tool to find who is most suitable.
If any thing they need some form of yardstick just to reduce numbers.