When Special Agent Cage is inspecting Reagan during the high-speed drive in limousine for wounds, the view through the windows shows protective tarping, giving away the fact the vehicle isn't actually moving. See more
Constitutionally, gentlemen, you have the President, the Vice President and the Secretary of State in that order, and should the President decide he wants to transfer the helm to the Vice President, he will do so. He has not done that. As of now, I am in control here, in the White House, pending return of the Vice President and in close touch with him. If something came up, I would check with him, of course.