IANAL, but my guess is the age and gender can be passed off IF United can convince a court that the FAs are in a entertainment role for these flights rather than being "primarily there for your safety". It's how Hooters and like can get away with only hiring female servers (although other positions in the restaurant can be filled by men), although on that note, Hooters Air did have separate roles for Hooters girls (serving on the plane) and Flight Attendants (there for your safety). The blond part will be much harder as that would have ties to race.
I'd expect the first thing United's lawyers are doing is looking at the percentage of FAs on these lists that are black/brown vs the FA group as a whole. We could probably guess how big that difference is (if there is one) by how quickly UA decides to settle.
EDIT: Want to caveat this entire post with a "assuming the lawsuit's allegation of UA's preferred FA lists being full of young blond women is correct"
Last edited by lowfareair; Sep 12, 2020 at 9:35 am