July 30th, 1939 (SUNDAY)
UNITED KINGDOM: The first production Boulton Paul Defiant, turreted fighter (L 6950) flies.
U.S.S.R.: Submarine K-51 is launched.
ITALY: The first of the Marconi class submarines, Regio Somm. Gugliermo Marconi is launched at the Monfalcone shipyards on the Adriatic.