In 1940, the 70th Congress passed Public Law 635, a 10,000 plane programme which included a provision for 48 non-rigid airships. However, based on a rise in U-boat activity during WWII, the number of blimps in flight would increase to 133 in total. 35,600 operational flights were made in the Atlantic and 20,300 in the pacific from 1942 - 1945. Navy Blimp SP-12 participated in the sinking of the last German U-boat used in WWII. After the war, the Navy decreased its blimp fleet, eventually ceasing used of the airships in the 60s.