I'm getting "Continuity of Govt" but could be wrong.
Secret C-20C "Senex" Aircraft
Three Air Force C-20C aircraft (85-0049, 85-0050, and 86-0403) based at Andrews AFB are operated by the Presidential Airlift Group (PAG) of the 89th Airlift Wing. The C-20C aircraft are a secret part of the COG program and are designed to move senior executives (Senex) quickly in the event of a national emergency.
The three C-20C aircraft are equipped with a comprehensive hardened communication system installed by E-Systems and designed to enable operations in a post-nuclear environment. Whenever the President travels away from Washington, a C-20C is positioned discretely at an adjacent airfield in case the President has to suddenly depart and Air Force One has been disabled.
https://whitehouse.gov1.info/continuity-plan/