Castle_Rock = Raven Rock (Site R)
[Site R? do they keep Jr hiding there?-JK]
They are not going to fly POTUS across country in an emergency.
They will go to Camp Davids mountain bunker
https://aboutcampdavid.blogspot.com/2011/08/raven-rock-mountain-complex.html
The Raven Rock Mountain Complex (RRMC), also known as Site R, is a U.S. military installation with an underground nuclear bunker near Blue Ridge Summit, Pennsylvania, at Raven Rock Mountain that has been called an "underground Pentagon".[4][5] The bunker has emergency operations centers for the United States Army, Navy, Air Force and United States Marine Corps. Along with Mount Weather Emergency Operations Center in Virginia and the Cheyenne Mountain Complex in Colorado, it formed the core bunker complexes for the US Continuity of Government plan during the Cold War to survive a nuclear attack.
https://en.wikipedia.org/wiki/Raven_Rock_Mountain_Complex
In The Event Of Attack, Here's How The Government Plans 'To Save Itself'
https://www.npr.org/2017/06/21/533711528/in-the-event-of-attack-heres-how-the-government-plans-to-save-itself