Originally Posted by
jrl767
FlightAware and FR24 show an Alaska 737MAX8 arriving BFI at 1105, one belonging to AJet at 1119, and a third belonging to Hainan Airlines at 1210
I’m guessing that OP is referring to the second one
a search for images of this jet showed a whitetail, but the below pic was a bit lower in the results

Yea that's got to be it. I was guessing they were going to start branding Atmos on the tails...

False alarm!