In 1948 he bought a controlling interest in RKO Pictures Corporation, sold the shares in 1953, bought the whole company in 1954, selling it again in 1955. He remained chairman of the board until 1957.

In the field of aviation he founded the Hughes Aircraft Company, Culver City, Calif., using the profits to finance the Howard Hughes Medical Institute. On Sept. 12, 1935, in an airplane of his own design, he established the world's landplane speed record of 352.46 miles (567.23 kilometres) per hour. On Jan. 19, 1937, in the same craft, he averaged 332 miles per hour in lowering the transcontinental flight-time record to 7 hours 28 minutes. Flying a Lockheed 14, he circled the Earth in a record 91 hours 14 minutes in July 1938. From 1942 he worked on the design of an eight-engine, wooden flying boat intended to carry 750 passengers. In 1947 he piloted this machine on its only flight—one mile.

Never an extravert, Hughes went into complete seclusion in 1950. As the holder of 78 percent of the stock of Trans World Airlines, he refused to appear in court to answer antitrust charges and thus lost control of the organization by default. In 1966 he sold his TWA shares for more than $500,000,000. His penchant for privacy and seclusion aroused unusual interest in his whereabouts and often entangled him in controversy. This culminated in 1971 in a scandal over what were purported to be his memoirs, which were bought for book and magazine publication at sums totalling $1,000,000. The manuscript, and letters concerning it supposedly written by Hughes, were subsequently found to be fraudulent and forged.

In his final years he abruptly moved his residence from one place to another (Bahamas, Nicaragua, Canada, England, Las Vegas, Mexico), arriving at each new destination unnoticed, taking elaborate precautions to ensure absolute privacy in a luxury hotel, and rarely being seen by anyone except a few male aides. Often working for days without sleep in a black-curtained room, he became emaciated and deranged from the effects of a meagre diet and an excess of drugs. He died on a flight from Acapulco, Mex., to Houston, Texas, U.S., to seek medical treatment.

After his death there arose considerable legal debate over the disposition of his estate. Several “wills” appeared, including one found in the offices of the Mormon church in Salt Lake City, but all were eventually declared to be forgeries.