The Mechanical Monsters (1941)

Released: 21 November 1941 (USA)
Directors: Dave Fleischer, Steve Muffati (uncredited)
Writers: Joe Shuster (comic strip created by: Superman), Jerry Siegel (comic strip created by: Superman) (as Jerome Siegel)
Stars: Bud Collyer, Joan Alexander, Jackson Beck

Superman battles a criminal mastermind and his robot army.
Trivia
The design for the flying robots was later given an homage by the brilliant Hayao Miyazaki twice! One was in a Lupin the III short, "Farewell My Beloved Lupin.", where it's used (as in this short) to steal. The second is in Laputa: Castle in the Sky.
Also given homage in 'Sky Captain and the World of Tomorrow (2004)'
This cartoon is the first Superman story in which Clark Kent changes into his Superman costume inside a phone booth.