What procedures are in place in the US for when multiple people in the line of succession are in the same place at the same time?

Question

What are the governmental procedures in the United States for important people (people in the chain of succession to the presidency) staying in the same place? Who can and who cannot fly together, etc. Where is this written down?

Answer 1

This refers to the "designated survivor" practice, which is not codified in law; rather, it is a choice made by presidents. There are no published details as to how Marty Walsh was selected as the 2023 "designated survivor". Historically, it was deemed to be a good idea during the Cold War, and after 9-11 it became a more rigorously followed practice. It is voluntary (the exact selection procedure is unknown and presumably highly variable) and not "written down".