Falling Sky by Rajan Khanna

Ben Gold lives in dangerous times. Two generations ago, a virulent disease turned the population of most of North America into little more than beasts called Ferals. Some of those who survived took to the air, scratching out a living on airships and dirigibles soaring over the dangerous ground. 

Ben has his own airship, a family heirloom, and has signed up to help a group of scientists looking for a cure. But that’s not as easy as it sounds, especially with a power-hungry air city looking to raid any nearby settlements. To make matters worse, his airship, the only home he’s ever known, is stolen. Ben must try to survive on the ground while trying to get his ship back.  

This brings him to Gastown, a city in the air recently conquered by belligerent and expansionist pirates. When events turn deadly, Ben must decide what really matters–whether to risk it all on a desperate chance for a better future or to truly remain on his own.