Harry S. Truman was the 33rd president of the United States, serving from April 12, 1945, to January 20, 1953. Born in Lamar, Missouri, in 1884, he commanded an artillery battery in France during World War I, served as a Jackson County judge and entered the U.S. Senate in 1935, where his wartime committee on waste in defense contracts made him a national figure. He became vice president in January 1945 and succeeded Franklin D. Roosevelt in April, only then learning the details of the Manhattan Project. His presidency took in the atomic bombings of Hiroshima and Nagasaki, the Truman Doctrine, the Marshall Plan, NATO, the Korean War and the National Security Act of 1947, which created the Air Force, the Central Intelligence Agency and the National Security Council. He passed away in 1972.

The flying saucer era began on his watch, and his recorded comments were brief. At a White House news conference on July 10, 1947, days after the Roswell announcement, a reporter asked whether he had seen any flying saucers; Truman answered, "Only in the newspapers," and likened the reports to the old moon hoax. In April 1950, while the president was in Key West, press secretary Charles Ross told reporters that Truman knew of no saucers held as a secret by the United States or any other country. A widely shared line in which Truman supposedly said saucers were "not constructed by any power on earth" has no known contemporary source, and researchers who traced it found no presidential news conference on April 4, 1950, the date usually attached to it.

A firsthand account came from his Air Force aide, Robert Landry. In an addendum to his Truman Library oral history, Landry wrote that in 1948 Truman directed him to report quarterly, after consulting intelligence officials, on whether any UFO reports carried strategic threatening implications. The reports were made orally, Landry said, and nothing credible or threatening was ever received.

Truman's name is central to the story of Majestic-12, an alleged committee said to manage recovered craft. In December 1984 researcher Jaime Shandera received an anonymous roll of film showing a purported 1952 briefing for President-elect Eisenhower and a memo dated September 24, 1947, in which Truman supposedly authorized Defense Secretary James Forrestal to proceed with "Operation Majestic Twelve." William Moore and Stanton Friedman promoted the papers, which listed Vannevar Bush and other senior officials as members.

The documentary record runs the other way. Truman's signature on the memo matches the one on a genuine October 1, 1947, letter to Bush, which critics read as a sign it was copied. White House and National Security Council spokesmen denied in 1987 that any such group existed. In 1988 the Air Force Office of Special Investigations told the FBI that no such committee had ever been authorized or formed, and the FBI declared the document "completely bogus." Truman's actual record, from the 1947 law that created the Air Force and CIA to the quarterly oral UFO briefings his aide later described, remains the starting point for the crash-retrieval timelines that still begin with his administration.