Skybreaker by Kenneth Oppel

A legendary ghost ship. An incredible treasure. A death-defying adventure.

Forty years ago, the airship Hyperion vanished with untold riches in its hold. Now, accompanied by heiress Kate de Vries and a mysterious gypsy, Matt Cruse is determined to recover the ship and its treasures. But 20,000 feet above the Earth's surface, pursued by those who have hunted the Hyperion since its disappearance, and surrounded by deadly high-altitude life forms, Matt and his companions soon find themselves fighting not only for the Hyperion—but for their very lives.