Other mistake: Wouldn't Thunderbird 1 leave some sort of burn marks on the pool side as it lifts off? The blast pattern is close enough to the sides.
Other mistake: When TinTin goes head to head with The Hood, she makes the catwalk spin 90 degrees anticlockwise. Alan is now on top of the catwalk when in fact he should still be on the bottom of the catwalk but on the opposite side.
Other mistake: When Transton notices the Guidance processor missing, the Hood quickly realises the kids have it and for some reason he's certain they're alive. But since they got the processor before escaping, they could have it when they supposedly got burned and killed.
Answer: I think that in the movie: Alan, Tintin & Fermat are 16, making Gordon 18, Virgil 21, John 23 and Scott 24.