The story I've heard from a reasonably reliable source:

1. The company is slightly OVERstaffed but pilots aren't staffed where they need to be (IAH 777 and IAH 756, specifically).

2. A lot of "surplus" pilots from the -400.

3. TK backed up because of the bumps.

All of that along with Kirby's claim of increasing block hours without additional hiring. The sky is not falling (yet), but frustrating to see classes cancelled.

Wait a week and we'll be back too hiring 1200 this year.