A bitter union strike began in May 1941, which was resolved without the angered Walt Disney's involvement in July and August of that year. As Walt Disney Productions was being set up as a union shop, Walt Disney and several studio employees were sent by the U.S. government on a Good Neighbor policy trip to Central and South America. The Disney strike and its aftermath led to an exodus of several animation professionals from the studio, from top-level animators such as Art Babbitt and Bill Tytla to artists better known for their work outside the Disney studio such as Frank Tashlin, Maurice Noble, Walt Kelly, Bill Melendez, and John Hubley. Hubley, along with several other Disney strikers, went on to found the United Productions of America studio, Disney's key animation rival in the 1950s.