Attrition and training?
 

In the latest update:

Attrition in 2017 = 60

Gone to other airlines = 35

Retired = 4

60 - 39 = 21

New hires = 180

What happened to these 21 guys? Are they training failures? If so, that's a terrible batting average for new hires and potential applicants should take note, if indeed these are training failures.

My understanding is that they are training terminations or resignations.

It may also be guys that resigned in training for classes at better paying airlines. I'm not sure we track guys that leave voluntarily while still in training. They are in the 21 but we don't have a why is my guess.