Well Denver has some pretty good windows as long as they dont have a reflection, my favorite is Terminal C, which is not a UA
concourse, but has NW
, US, DL
, ATA, AS
and maybe a couple others, if you head over to A, you can get on the Bridge to do some spotting, and right where the bridge starts at A there are a couple places that are kinda secluded in a little bit of a way that offers many of the pictures that you see on A.net from the bridge.