...is also known as a USSS code for the hand off...
...AF1 now has POTUS...
...not sure if it applies here though...
From the Q post mention of ‘wheels up’ , I thought this definition was good as well —from the Urban dictionary
wheels up
the time or point when a plan or operation is executed. it comes from the military to describe when a plane lifts off to start a deployment, at that point an operation is considered hot (officially started).