If it's like the article describes, then there should be no recourse from the union.

Sounds like FAs on reserve pay were not close enough to their base to get to work on time, which basically means they rolled the dice and hoped they wouldn't get called up. Honestly, if you're getting paid to literally do nothing other than be close the base and you can't even do that then the termination is warranted. I'm guessing this is not happening to first/one time offenders but who knows.