"Airborn" by Kenneth Oppel is a story of possibilities. This work of fiction portrays what the world might have been like had the aircraft as we know it not been invented. Instead, airships of the day use a fuel called hydrium and resemble hot air balloons more closely than they do airplanes of today. The story centers around a cabin boy named Matt Cruse who works aboard the airship Aurora, just as his father before him had. When his father is killed in a freak accident, Matt is given a job by the captain of the ship, enabling him to continue to support his mother and two sisters.

The story begins with the discovery of a hot air balloon, adrift and in distress. The balloon's pilot, Benjamin Molloy, lives long enough to ask Matt if he'd seen 'them', and dies shortly after realizing Matt had not. A year later, Molloy's granddaughter Kate de Vries follows the closest flight path she can in the hopes of seeing the miraculous creatures he describes in his journal for herself. An unexpected confrontation with air pirates causes the Aurora to crash land on the very island Molloy described and drew so carefully. When Kate realizes her good fortune, she is determined to find evidence of the creatures her grandfather described, and restore his good name in the scientific community. She convinces Matt to accompany her into the woods in search of them, despite Matt's objections and reservations. When they encounter an aggressive, jumping snake, they take refuge in a tree, and climbing high enough to avoid the snake, they inadvertently discover a skeleton of the creature Kate's grandfather had described and drawn. Strong willed and determined, Kate defies her chaperone again and again, initially to explore the forest in the hopes of discovering evidence of the creature, then again when returning to collect the skeleton. Their escapades turn out to be fortuitous for the rest however because when they are caught in a topical storm and take refuge in a cave they inadvertently discover a source of hydrium that will enable the Aurora to fly again. As they refuel, Kate drugs her chaperone who had insisted on confining Kate to their stateroom to keep her from gallivanting again. She makes one last trip into the woods in the hopes of capturing a photograph of the creature before the ship is ready to leave. Matt is one of two who are sent to find her, and the photography session turns into a flight for life. While fleeing the creature who turns out to be less cuddly and more carnivore, Matt and Kate stumble right into the pirate's home base. They must escape, and then help to rescue the Aurora from the pirates who have taken control of her a second time. An exciting battle for control of the airship ensues and with a little bit of help from a flock of Cloud Cats, Matt helps to regain control of the ship and direct the authorities to the pirate's hideout. Kate manages to restore her grandfather's good name, touring with the proof that a previously undiscovered creature exists and earning the right to a university education.