Brand new factory sealed stand-alone dvd is Out Of Print (OOP) and no longer available. One of only two feature length stories based on the hit TV series with Supermarionation (live action puppets) and great minatures. Now only available as a pricey double feature.
THUNDERBIRD 6 is more coherant as a story of the two, with Lady Penelope, Parker, Alan, and Tin-Tin taking a round-the-world cruise on an anti-gravity airship designed by International Rescue's resident genius Brains as an evil scheme by a villain (the Black Phantom) who looks like a bewigged hood (but has a differant voice because Ray Barrett was unavailable) sets out to lure Thunderbirds 1 & 2 into a trap.
With a caper-style plot and more bizarre 'Avengers'/'Prisoner' like sets (themed staterooms in the airship), but carried over from 'Captain Scarlet' is a Bondian ruthlessness as we finally see actual deaths resulting from disaster or villany. Especially striking are shots of Skyship 1 cruising against a sunset as the murdered crew are dumped one by one into the sea.
An apparent sub-plot has patriarch Jeff Tracy insisting that Brains design a new Thunderbird but rejecting all his hi-tech designs, with the final wreck of the skyship prompting the inventor to take to the field in an outmoded biplane which becomes Thunderbird 6.
Perhaps the most exciting "stunt" in the International Rescue canon is Brains first attempt at landing on the upper hull of the airship, touching down but plunging over the edge. Also striking is a shoot-out amid the revolving metal circles of the anti-gravity engine.