Botox One or Ketchup One. No flaming please it is just a joke.
More to the point - No special call sign until he is sworn in. If Air Force One takes off with the outgoing president (who may that be this year?) before the swearing in occurs then the call sign is still AF
One. If the swearing in occurs while AF1 is still in flight heading to TX
once the new president is sworn in AF1 changed call sign in mid-flight to AF
or SAM followed by the reg number. If I remember correctly this occured when Nixon departed for California after his resignation which became effective while he was in flight. The reverse occured with Johnson who was sworn in on AF1. Other thoughts?
Fly me to the moon... but not through LHR!