United plane is a 777
737 engines have a shallower design on the bottom part, like it's been flatenned. You may search pics with the plane facing straight at you and you'll get what I'm saying. Triple seven engines are huge and they have a very distinct design on the aft cone, very pointy. 787s also have these cones, but the engines are smaller and the nacelles have a 'wavy' detail. United flies 777s to long haul Asian destinations, like Shanghai PVG / Hong Kong HKG
The window size/letter size ratio also fits the 739. At first it looked like something else to me, good job anon.