FAB is one of Lady Penelope Creighton-Ward's many yachts.
Penelope and Parker took the yacht to Tracy Island, with FAB 1 stored in its cargo bay, after being invited there by Jeff Tracy in order to visit the International Rescue headquarters.
Sometime later, FAB would seemingly either evolve into, or be replaced by, FAB 2.
FAB made only one appearance, in the Thunderbirds 1965 adaptation of Introducing Thunderbirds. While there was a yacht in the original story, it was never identified in dialogue.
FAB 1 in the ship's cargo hold
Exterior