Originally Posted by
jsloan
I'm tempted to agree, except that the OP went out of his way to say that he does attempt to engage with the FAs at exit and gets ignored.
OP: I'm white, my wife is Filipina, and I've never noticed what you're saying, nor has my wife ever mentioned it. "Goodbye" seems hit or miss to both of us.
I suggest changing up your routine; if you're Chinese (guessing based on your comment about your last name), say 'zai jian' or 'zoi gin' and see what reaction you get. Or, just say "I'm right here, you know," and laugh, whenever it happens.
I find it difficult to believe that UA FAs suddenly turn racist,
en masse, only when you're leaving the plane, so I imagine there must be another explanation. (Honestly, 6'1" and Asian might actually be the reason, especially if your height is mostly in your legs. You may be catching them off guard after they've interacted with you while seated the whole time). Why that wouldn't apply to DL, I can't say, except that DL has a reputation for having better service in general. (That doesn't match my experience, but I don't fly to/from EWR much).
Defending UA twice in one day? Are you feeling OK? 
From my read of the OP: I would guess if there is a there there, it's not that the FA's are in general actively hostile to people of Asian appearance — rather that, for some reason, the FA's have some level of discomfort for quick interaction with such people. And for some reason it happens more commonly with UA.
Maybe UA's large TPAC network and *A agreements mean they see more non-American / non-English-language Asians and have more numerous awkward interactions with them, so they default to silence out of uncertainty. Maybe attendant training doesn't emphasise greeting each passenger, and they don't as regularly stay 'on' during boarding/alighting as DL attendants do. Those are speculation on my part.
Or maybe OP is mistaken in his perception. But honestly it seems like a convincing accounting to me. It's just that after noting the observed experiences, it's hard to figure out where to go next. (Maybe the other airline.)
aside: the changed text colour palate is really messing with my quote technique.
