President Richard Nixon’s decision to mine North Vietnamese harbors is condemned by the Soviet Union, China, and their Eastern European allies, and receives only lukewarm support from Western Europe. The mining was meant to halt the massive North Vietnamese invasion of South Vietnam that had begun on March 30.

In the continuing air war over North Vietnam, the United States lost at least three planes and the North Vietnamese 10, as 150 to 175 American planes struck targets over Hanoi, Haiphong, and along rail lines leading from China. Lt. Randy Cunningham and Lt. Willie Driscoll, flying a Navy F-4J Phantom from the USS Constellation knocked down three MiGs in one combat mission. Added to two previous victories, this made Cunningham and Driscoll the first American aces of the Vietnam War (and the only U.S. Navy aces of the war).

Also on this day: Air Force Capt. Charles B. DeBellevue of the 555th Tactical Fighter Squadron, flying with Capt. Richard S. Ritchie in a McDonnell Douglas F-4D, records his first aerial kill. Later, DeBellevue recorded four additional victories with pilot Ritchie–both men achieved the designation of ace (traditionally awarded for five enemy aircraft confirmed shot down in aerial combatt). In August, DeBellevue, flying with Captain John A. Madden, Jr., shot down two more MiGs, becoming the leading American ace of the Vietnam War.