Boat One

Boat One was the presidential aircraft of UNIT, created as part of an international agreement on incursion protocols. Under this agreement, in the event of a full-scale invasion a President of Earth with complete authority over every nation state was immediately inducted, it was decided the only practical candidate for this role was the Doctor.

This induction was performed during an invasion of Earth by an army of Cybermen created from the dead by a female incarnation of the Master via the 3W organisation. Having stumbled upon the invasion, the Twelfth Doctor was taken aboard by UNIT and inducted as Earth president. (TV: Death in Heaven)