Ruth Plumly Thompson 
Ozoplaning with the Wizard of Oz 

Ozoplaning with the Wizard of Oz is the thirty-third in the series of Oz books created by L. Frank Baum and his successors, and the nineteenth and last written by Ruth Plumly Thompson. The Wizard unveils the newly created ozoplanes, and a chaotic flight takes them to a previously unexplored sky-country called Stratovania.