The 12500 lb rule.

[upndsky]

I would think that an airline would only consider an alien with a green card, since a work visa expires at some point (max of 6 years, I think). I can't imagine a company investing the time and money into a pilot who they know is going to have to leave the country at some point down the road. Green card holders don't face that issue and can travel just as freely as US citizens.

BTW, the site at https://www.flightschoolcandidates.gov is up and running again.