Both ASA and Comair were owned by Delta at one point and represented by ALPA and they no longer operate. I don't think a union helps an airline be more strong in times of economic uncertainty. A lot of people may argue that a Union might actually be worse for an airline in an economic downturn. There were other ALPA carriers owned by majors that no longer exist at all. Skywest is still here.

The majors seem to file bankruptcy every 10-20 years and the regionals they own are negatively effected when that happens.