In "Trapped in the Sky", master criminal the Hood plants a bomb on board the new atomic-powered airliner Fireflash before it departs on its maiden flight.

While planning the episode, the Andersons drew inspiration from Gerry's memories of his National Service in the RAF, during which he witnessed the fatal crash of a Mosquito aircraft and the emergency landing of a damaged Spitfire.

To save studio space, special effects director Derek Meddings filmed the rescue of Fireflash on a static set using a system of looping canvasses instead of a miniature runway.

Lew Grade, the Andersons' financial backer, was so impressed by the production that he ordered APF to re-write and extend every Thunderbirds episode from 25 to 50 minutes so that the series would fill a one-hour TV timeslot.

Travelling to London International Airport, he plants a bomb within the landing gear hydraulics of Fireflash, a new atomic-powered hypersonic airliner departing for its maiden flight to Tokyo.

After Fireflash takes off, the Hood anonymously calls air traffic control to reveal his sabotage, warning Commander Norman that the bomb will detonate on landing.

ATC commandeers a military plane that docks with Fireflash in the air, allowing Lieutenant Bob Meddings to gain access through a service hatch and attempt to remove the bomb.

After giving Kyrano a clean bill of health, the doctor notes the Fireflash incident and says that he would be honoured to shake International Rescue's hand.

[9][16][14] Meddings' original design sketch for Fireflash indicated that the airliner was flown by BOAC; in the completed episode, it is operated by the fictional "Air Terrainean".

[18] The Fireflash landing sequence presented Meddings with the challenge of having to film a scale runway inside a relatively small effects studio that offered little scope for camera movement.

[19] Rather than build a miniature runway and move the camera, his solution was to isolate the basic set elements (the grass verge in the foreground, the sky background and the runway separating them) and construct separate loops of canvas, each painted to represent one element; the canvasses were then fitted to rollers that were run at speeds proportionate to their distances from the camera, creating the illusion of a dynamic shot on a continuous set.

[19][20][21] The crash of the remote-controlled Elevator Car was originally an error, caused when the wire pulling the scale model unexpectedly snapped in the middle of a shot.

[9][19][20] The original footage of the car losing control was then supplemented by an additional shot that shows it hitting the stationary aircraft and bursting into flames.

[39] Mike Fillis of TV Zone and Cult Times magazines considers the episode a "tour de force" and a series highlight, describing the story as "riveting" and the bomb plot as "very topical".

"[42] Jon Abbott of TV Zone judges the tension "of feature-film quality" but also comments that "the total lack of security for the Fireflash nags at the viewer."

He calls the idea of a nuclear-powered aircraft "wonderfully pointless", adding that it "could only have been dreamed up in the '60s, when science was unquestioned and the possibility of building something so silly always outweighed any safety considerations.

[3][41] Reviewing the release for website DVD Verdict, David Gutierrez gave the episode a score of 95 out of 100, calling the rescue "amazing" and adding: "Television rarely has moments as exciting as the Fireflash attempting a forced landing.

[44] A BBC Online retrospective describes Fireflash as a "beautifully-envisioned, Concorde-like craft" and compares the London Airport lounge to "a set from a Dean Martin movie".

[46] In a review of the Thunderbirds soundtrack, BBC Online's Morag Reavley praises the incidental musical piece "Fireflash Landing", describing it as one of several "catchy, pulse-quickening tunes" that "come fast and furious.

"[47] Vincent Law of fanzine Andersonic argues that the episode's status as a "pilot" is not detrimental to the plot, which he regards as being based on "advanced technology, upon which the characters are reliant, going awry."

The first of these was an audio play, narrated by Shane Rimmer in character as Scott Tracy, which was first released as the Century 21 mini-album Thunderbird 1 (code MA 108) in 1966.

[50] First broadcast on 25 April 2015, the remake episode re-uses characters and plot elements from the original, including the Captain Hanson and the rescue involving the Elevator Cars.