Skybreaker - Kenneth Oppel

Matt Cruse has been accepted at the Airship Academy, his days as cabin boy over for the moment. He has difficulty settling down to life on land, but is helped by the fact that Kate is in Paris too.

During a training flight aboard the freighter
Flotsam , Matt helps save the ship when it is caught in a deadly storm over the Indian Ocean, and thrust to dangerously high altitudes. There, Matt spies a frozen airship, drifting aimlessly at 20,000 feet - it's the legendary ghost ship Hyperion . Rumoured to be carrying great wealth, the Hyperion left harbour fifty years ago, but never reached her destination. No wreckage was ever found ... until now.

And it is not just gold the Hyperion is reputed to carry, but a collection of strange zoological specimens. Kate is desperate to recover them, and she and Matt embark on the most dangerous of treasure hunts ...