Hughes enjoyed a highly successful business career beyond engineering, aviation, and filmmaking; many of his career endeavors involved varying entrepreneurial roles. The Summa Corporation was the name adopted for the business interests of Howard Hughes after he sold the tool division of Hughes Tool Company in 1972. The company served as the principal holding company for Hughes' business ventures and investments. Though primarily involved in the aerospace and defense, electronics, mass-media, manufacturing, and hospitality industries, it has also maintained a strong presence in a wide variety of industries including real estate, petroleum-drilling and oilfield services, consulting, entertainment, and engineering. Much of Hughes' fortune later went to philanthropic causes, notably supporting health-care and medical research.
Originally known as Summa Corporation, the Howard Hughes Corporation formed in 1972 when the oil-tools business of Hughes Tool Company, then owned by Howard Hughes Jr., floated on the New York Stock Exchange under the "Hughes Tool" name. This forced the remaining businesses of the "original" Hughes Tool to adopt a new corporate name: "Summa". The name "Summa"—Latin for "highest"—was adopted without the approval of Hughes himself, who preferred to keep his own name on the business, and suggested "HRH Properties" (for Hughes Resorts and Hotels, and also his own initials). In 1988 Summa announced plans for Summerlin, a master-planned community named for the paternal grandmother of Howard Hughes, Jean Amelia Summerlin.
In 1972, during the cold war era, Hughes was approached by the CIA through his longtime partner, David Charnay, to help secretly recover the Soviet submarine K-129, which had sunk near Hawaii four years earlier. Hughes' involvement provided the CIA with a plausible cover story, conducting expensive civilian marine research at extreme depths and the mining of undersea manganese nodules. The recovery plan used the special-purpose salvage vessel Glomar Explorer. In the summer of 1974, Glomar Explorer attempted to raise the Soviet vessel. However, during the recovery a mechanical failure in the ship's grapple caused half of the submarine to break off and fall to the ocean floor. This section is believed to have held many of the most sought-after items, including its code book and nuclear missiles. Two nuclear-tipped torpedoes and some cryptographic machines were recovered, along with the bodies of six Soviet submariners who were subsequently given formal burial at sea in a filmed ceremony. The operation, known as Project Azorian (but incorrectly referred to by the press as Project Jennifer), became public in February 1975 after secret documents were released, obtained by burglars of Hughes' headquarters in June 1974. Although he lent his name and his company's resources to the operation, Hughes and his companies had no operational involvement in the project. The Glomar Explorer was eventually acquired by Transocean and was sent to the scrap yard in 2015 during a large decline in oil prices.
Shortly before the 1960 Presidential election, Richard Nixon was alarmed when it was revealed that his brother, Donald, received a $205,000 loan from Hughes. It has long been speculated that Nixon's drive to learn what the Democrats were planning in 1972 was based in part on his belief that the Democrats knew about a later bribe that his friend Bebe Rebozo had received from Hughes after Nixon took office.
Hughes was living in the Intercontinental Hotel near Lake Managua in Nicaragua, seeking privacy and security, when a magnitude 6.5 earthquake damaged Managua in December 1972. As a precaution, Hughes moved first to a rather large tent, facing the hotel, then after a few days there to the Nicaraguan National Palace and stayed there as a guest of Anastasio Somoza Debayle before leaving for Florida on a private jet the following day. He subsequently moved into the Penthouse at the Xanadu Princess Resort on Grand Bahama Island, which he had recently purchased. He lived almost exclusively in the penthouse of the Xanadu Beach Resort & Marina for the last four years of his life.
In 1972, author Clifford Irving caused a media sensation when he claimed he had co-written an authorized autobiography of Hughes. Hughes was so reclusive that he did not immediately publicly refute Irving's statement, leading many to believe the Irving book was genuine. However, before the book's publication, Hughes finally denounced Irving in a teleconference and the entire project was eventually exposed as a hoax. Irving was later convicted of fraud and spent 17 months in prison. In 1974, the Orson Welles film F for Fake included a section on the Hughes biography hoax, leaving a question open as to whether it was actually Hughes who took part in the teleconference (since so few people had actually heard or seen him in recent years). In 1977, The Hoax by Clifford Irving was published in the United Kingdom, telling his story of these events. The 2006 film The Hoax, starring Richard Gere, is also based on these events.