The British government has instructed President Joe Biden and other dignitaries attending Queen Elizabeth II's state funeral next week .
Politico has obtained official planning documents for the solemn service on September 19 that encourage presidents, monarchs, and other heads of state .
Those who have worked on presidential security and preparation in the past say it won't happen.
"I can't envision any conditions where the USSS (Secret Service) would agree to any of that," said Anita McBride, who served as assistant to President George W. Bush.
The Secret Service did not want to talk about the president's journey or the security measures that will be in place.
Air Force One is the vehicle of choice for Biden's arrivals whether he is travelling locally or internationally.