Vraciu's most successful day as an aviator occurred on June 19, 1944, during the First Battle of the Philippine Sea, also known as the "Great Marianas Turkey Shoot." Despite a malfunctioning supercharger, he intercepted a formation of Japanese dive bombers and destroyed six in a period of eight minutes. After Vraciu landed, the ordnancemen on "Lexington" discovered that he had used only 360 rounds of ammunition. (On average, each of the six kills followed a burst lasting less than five seconds.) On June 20, 1944, while escorting bombers in an attack on the Japanese Mobile Fleet ("Kido Butai"), Vraciu downed his nineteenth plane, making him the leading U.S. Navy ace, although he held that title for only four months. Vraciu was nominated for the Medal of Honor for his actions at the First Battle of the Philippine Sea; however, when the nomination reached the desk of Admiral George D. Murray at Pacific Fleet Headquarters in Hawaii, it was downgraded to a Navy Cross. Vraciu returned to the United States on leave in August 1944, and was promoted to a lieutenant upon his return to San Diego, California. Until he received orders for a new combat assignment, Vraciu made public appearances to promote the U.S. Navy in the United States.