I’d tell that anon to look in Viet Nam.
POTUS is in the back seat. :)
The plane is a UNITED STATES NAVY C-40 Clipper.
I dont think its a United Airlines plane.
There is a good pic of one at Wikipidia - Everything matchs except the Navy paint job has a black line under the gold line. But maybe they changed their paint jobs.
Anyone can drive a car up to a plane at any airport FBO (Fixed Base Operator) and also on any Military Airbase... its a very common way to unload bags and people... All you need is someone to open the gate. I was a Flight Engineer for the Army and almost always we would drive out to our plane.
Also when not deployed, all military transport aircraft are pooled together and scheduled as needed to support any and all branches, and even government agencies.
Pocketdoor