On May 15, 1928, Walt Disney screened the Mickey Mouse animated short Plane Crazy. 

The 6-minute film was animated entirely by Ub Iwerks.

Plane Crazy – Mickey and Minnie
From Mickey’s Portrait Gallery series
Issued by Nevis post office September 11, 1992
Artwork: Walt Disney Co

Iwerks completed Plane Crazy in 2 weeks, averaging 700 drawings each day. The film was screened without a soundtrack and before a small test audience. It failed to gain a distributor. When Steamboat Willie, the first Mickey film, was released November 18, 1928, it proved to be enormously popular and launched Disney’s career.  

Story board panels from Plane Crazy
Iwerks, Ub, 1901-1971, artist, from 1928
drawing: graphite with color pencil ; sheet 30.2 x 23.9 cm.
Courtesy Library of Congress Prints and Photographs Division Washington, D.C. 20540 USA http://hdl.loc.gov/loc.pnp/pp.print

By the time Plane Crazy was ready for general release, Disney had released 2 more animated shorts The Gallopin’ Gaucho and The Barn Dance (1929). Plane Crazy was released, with a soundtrack (recorded October 26, 1928), on March 17, 1929, to widespread popular approval.