F.A.B.

Not to be confused with the audio story, or the spy organisation.

A typical International Rescue communication (Download Danger!)

F.A.B. is the codeword used by International Rescue agents as a means of acknowledgement, serving a similar purpose to "Roger". Although pronounced as individual letters, it does not stand for anything. The codeword was suggested by Grandma Tracy as a short, precise, and unique sounding term of acknowledgement, and based it off 'fabulous', which had been a much used phrase long ago.

Link 13, International Rescue's head of communications, also put forward that F.A.B. was occasionally used to mean a mission instruction had been Filed by onboard systems, Actioned by the agent, and Banked at the Tracy Island mainframe.

Behind the Scenes

F.A.B. never stood for anything, ever. Like Grandma Tracy, the real-world production team behind Thunderbirds based it off of 'fabulous', which was a popular byword during the 1960s. Although that never stopped people from trying to fit meaning to them - the letters are often, but incorrectly, thought to mean either 'Fully Acknowledged Broadcast' or 'Fully Advised and Briefed'.

The confusion regarding the codeword would eventually be brought in-universe, at least in the world of Thunderbirds Are Go!. In Extraction, after Robert Williams and his son are rescued from a methane pit, he directly asks what the codeword means, but, to his bewilderment, is only met with laughter as a response. In fact, Thunderbirds Are Go! would later introduce a second codeword - R.A.D., used by Brains, which was similarly based off of 'radical'.