More important than the shadow, check out the windows and the spacing of the letters on the United plane. I have been digging for a while and cannot find that particular type of plane in the fleet. Most United Boeing/Airbus have windows evenly spaced under the UNITED logo. Any United employees that can identify the plane? PLANEFAGS activate!
Also, USSS known to use Chevy Suburbans, but the stereo/nav console screens it is hard to tell what is on the screen. If that is a backup camera, there is a half red/white sign in the pic.