"Trapped in the Sky" was originally filmed as a 25-minute pilot in late 1964. 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. Well received on its first broadcast, "Trapped in the Sky" is widely regarded as one of the best episodes of "Thunderbirds". It was adapted into an audio play in 1966 and had its first UK-wide showing in 1991 on BBC 2. It was later re-made as "Fireflash", the fifth episode of the remake series "Thunderbirds Are Go".