Obviously a regular staffer, perhaps intrigued by the massive shadow of the aircraft as it completes the final few minutes of a trip, and they decided to join the flights together with a visual constant. I'm sure that personal cameras and the security environment surrounding AF1 don't mix too well, so perhaps this was a way to remember the hundreds of trips and thousands of hours aboard AF1.
I realise that for some it will be WTF as it's not a photo of the outside of an aircraft, but for many others the only view from a window seat during many a flight.
SHJ