This seems like an obvious question but why does one guy and his staff need a more than 400 passenger plane?
Technically speaking? He probably doesn't, but that doesn't really matter. Like it or not, the VC-25 is part of the image that the presidency presents to the rest of the world. If you want to present an image of strength and the supremacy of the American Ideal, showing up in a European aircraft is not the way to do it. Also, showing up in a smaller aircraft (787 or 777) doesn't help either. Like it or not, it's partially dick waving, and the 747-800i is really the only choice.