In the 'Fit to Fly' programme, the Lab Rats - Mike Leahy and Zeron Gibson - face the most intense experience of their lives. They compete for a ride in the awesome F-16, the US Air Force fighter plane that can manoeuvre at a terrifying 9g. With a force 9 times their own bodyweight pushing down through their heads, all their blood rushes to their feet. If they do nothing, their brains will be starved of oxygen. They have to learn a special breathing technique just to remain conscious.

In Top Gun, Tom Cruise didn't use this technique. Under the g-forces of combat flight he would have blacked out and lost control of his aircraft. By rights, he should be dead. But how will the Lab Rats cope, and who will win the flight of a lifetime?

The Lab Rats' training starts at the stunt flying school run by former Red Arrow pilot, Andy Cubin. Andy gives the Lab Rats a taste of what lies ahead. Dramatic flying and stomach-churning spins in gyroscopes make the Lab Rats doubt whether the F-16 is a prize they want to win. "It'll turn you to blubber and you'll be crying for your mummy," warns Andy.

Then it's off to New Mexico, USA, to face the military centrifuge training that all fighter pilots must pass before they can fly. The Lab Rats must survive a bone-crushing 9g spin. "At 9gs it's like an elephant is on your chest," says centrifuge tutor, Lt Vikki Thompson. Which of our Rats will become a G-Monster and win the flight of their lives in an F-16 fighter?