The One with... the fashion show in the sky.
Under his alias "Mr Hackenbacker", Brains has designed the Skythrust, a new type of jetliner. While it is undergoing final tests over London, Lady Penelope is asked to visit her designer friend, François Lemaire, in Paris. This designer has developed a new, revolutionary fabric, which he has named "Penelon" after everyone's favourite London Agent. Taken aback by such an honour, Lady Penelope nevertheless maintains her wits enough to determine that Lemaire is under intense surveillance. Convinced of the threat to this new fabric, Lady Penelope arranges for the first fashion show to take place aboard the Skythrust.
However, the evil masterminds determined to steal Penelon don't let that stop them, and hijackers take over Skythrust. The Thunderbirds respond instantly to Lady Penelope's distress call and, at Brains' urging, use a non-explosive rocket to disable Skythrust's landing gear. The pilots warn the hijackers of the explosive consequences of attempting a landing with nearly-full fuel tanks on a rough strip in the middle of the Sahara with no landing gear. The hijackers agree to return to London, where the Skythrust performs a no-gear crash-landing at Heathrow. Fortunately, Brains' innovation - an ejectable fuel supply - prevents Skythrust from going off like a bomb, making it unique amongst aircraft in the Thunderbirds universe.
- Always Camp: Francois Lamaire is a fashion designer. So naturally, he has glittery eyeshadow and speaks with an outrageous accent.
- Being Watched: Nearly everything in Lemaire's penthouse is bugged. There are telescopes pointed at it, there are microphones in the sugarcubes, and his pen actually records and transmits what is being written with it.
- Cool Plane: Skythrust.
- Coming in Hot: Skythrust has to land without landing gear.
- Episode on a Plane: The new Skythrust is one of the two main elements of the plot, and a great part of the episode takes place on board the Skythrust.
- Fashion Show
- Impossibly Compact Folding: Penelon has this ability; even a complete dress made of penelon can be folded to fit into a matchbox.
- The Mole: Madeleine.
- Properly Paranoid: Lady Penelope suspects from the start that Francois's rivals might be spying on him, so she urges him not to say anything about this new invention untill she has thouroughly searched the room. Her suspicions are correct, as she discovers one spy tool after another.
- Secret Identity: Brains' alias Mr. Hackenbacker.
- Interestingly, both the 2004 movie and the 2015 revival series use Hiram Hackenbacker as Brains' real name.
- Secret Ingredient: Lemaire's invention Penelone, and the Skythrusts innovation against explosions during crash landings.
- Stuff Blowing Up: Notably averted. This may stand to be the only Thunderbirds episode where the Cool Plane Of The Week is not blown up.