Our Chains Unseen - The Flight of the Lady Firene, #4

Fleet Manteios never wanted to be captain of the airship Lady Firene. Her brother has been mortally wounded, though, leaving her in charge of their beloved ship. Her first job? Find a way to do the impossible and save Daryus' life. Reunited with Shan, himself on the run, she heads east. She hopes she'll find a magical cure for her brother amongst Shan's dangerous former masters - if she can reach them.
The eastern seas are being plagued by unnatural storms, and a captive magician seems to be behind them. Leaving Fleet with a choice. With Daryus' time running out, she can search for a cure in lands she knows, or risk it all to follow the magician and untangle the chains around him. That way lies a whole new world, stranger and more dangerous than any skies she's flown before. Succeed, and she'll find someone powerful enough to save Daryus - but fail, and she'll lose everything she loves.