Revealing mistake: When Thunderbird 3 lands in London, the jets do not burn the grass they land on.
Revealing mistake: When the kids run away from the crooks on Tracey Island they roll down a hill into a lagoon or so. Look carefully and you can see the persons rolling down the hill are adult stand-ins.
Answer: I think that in the movie: Alan, Tintin & Fermat are 16, making Gordon 18, Virgil 21, John 23 and Scott 24.