The second son of Jeff Tracy (founder and financier of International Rescue), John was named after astronaut John Glenn.[1] Sources vary in the canon of the Thunderbirds series as to John's age and birth date, although one written source suggests that he was born on 28 October 2041 - even though this would make him the third son.The majority of sources and two decades of Thunderbirds calendars cite John's birthday as October 8 and he is 25 years of age. Chris Bentley, author of 'The Complete Book Of Thunderbirds' erroneously cited Gerry Anderson as the source of the misinformation about the birth order of the Tracy brothers but later admitted that he was using the order of the brothers as shown in the credits. Most source books on Thunderbirds prior to the 'Complete' book noted that the birth order matches the number of the Thunderbirds ships, save that the third brother (John) and fifth brother (Alan) trade shifts aboard their respective crafts.
John is a noted scholar of astronomy and has authored several popular astronomy textbooks. He is a graduate of Harvard University with a degree in Advanced Telecommunications. [3] John's quiet intellectual nature and interest in astronomy make him the natural choice for the solitary life as the occupant of space station Thunderbird 5, monitoring for distress calls from around the world. He has only ever been seen physically involved in a rescue during the episode "Danger At Ocean Deep," although dialogue at the end of that episode suggests that he has already been on various (if unseen on-screen) missions. According to Carlton Books 'Lady Penelope's Secrets,' John is known to be exceedingly patient, kindly and gracious and possessed of both great intelligence and poise as gifts inherited from his talented mother.