hdgbug is correct about the training failure definition and also about the fact that the company has option but is not required to discharge a probie after his second bust.

Sadly, the failure rates are kept secret by the company and by our own union. I have asked what's the failure rate a couple times but I never gotten a straight answer.

And no the company is not known for busting people for no reason. Here's another example, did you know that if a pilot is not recommended after 2 IOE blocks then it's a training failure per CBA? When I was going through IOE I asked the training captain is that for reals, am I a toast if I don't finish in 2 blocks? And he said Hell no, a lot of people needed extra IOE blocks and not one of them got the boot. In fact, the company was even willing to offer extra sims to people who were struggling in the IOE, as long as they had the right attitude and were willing to own it.