Quite a few of my brothers and myself from IAM-AW local 709 would beg to differ,When we were laid off delta hired us (and some who were not laid off).
I am sure there are exceptions but from what I have seen especially from the former DL managers that work the line here I can tell you the vast majority hire former DL mechanics or other mechanics with non-union backgrounds. Whereas long time former FedEx managers in the hanger or outstations will hire based on experience regardless of union affilation