Envoy, PSA, and Piedmont all get flight benefits on AA, with the same priority as mainline so that's very good.
Endeavor gets flight benefits on Delta. On mainline Delta, they get a lower priority than mainline employees but higher than other Delta Connection Employees.
Republic gets UA, DL and AA.
SkyWest is also hiring E3 visa holders and depending on base and equipment determines what benefits you get. All pilots get United. All CRJ pilots get Delta and depending on base, E175 pilots get Delta. Depending on base CRJ pilots can also get AA, and e175 pilots can get Alaska. Priority on mainline is same as Republic. On SkyWest operated flights, you get high prioirty. All SkyWest employees get SkyWest operated Alaska flight benefits as well.