USS Franklin D. Roosevelt (CVB-42, later CVA-42 and CV-42) was a Midway-class aircraft carrier of the United States Navy, the second of the three ships in her class. She was commissioned at the New York Naval Shipyard on Navy Day, October 27, 1945. On July 21, 1946, she became the first American carrier to operate an all-jet aircraft, and in 1950 she became the first carrier to take nuclear weapons to sea. She spent most of her career in the Mediterranean, making 20 deployments there that helped shape the Sixth Fleet. She was decommissioned on September 30, 1977, sold in 1978 and scrapped at Kearny, New Jersey.

The carrier's most widely cited UFO report came during Operation Mainbrace, the NATO naval exercise held off northern Europe from September 14 to 25, 1952, in which she served as flagship of a fast carrier task force. On September 20, the American newspaper reporter Wallace Litwin, photographing flight operations aboard her, saw pilots and deck crew watching a silver sphere that seemed to follow the fleet, and shot four color photographs of it. He assumed it was a weather balloon, but the ship's executive officer found that none had been released, and the nearby carrier Midway reported none either. Edward Ruppelt, who headed the Air Force's Project Blue Book, later wrote that the photos "turned out to be excellent," that Naval Intelligence checked every nearby ship without finding anyone who had launched a balloon, and that the crew were divided over whether the object was one. RAF crews in England reported similar silver discs during the same exercise.

The ship's UFO history was later gathered by one of her own sailors. Chester C. Grusinski, who served aboard from 1958 to 1960, saw an unidentified flying object at Guantanamo Bay, Cuba, in 1958 and went on to research sightings by the carrier's crew. His papers at East Carolina University's Joyner Library include correspondence with former crew members, some describing UFO experiences aboard and others denying any knowledge of them, letters with government agencies, his drawing of the 1958 sighting and color slides from the Mainbrace sighting.

In 2026 the researcher Richard Dolan revisited the carrier in a series of videos, presenting the 1952 case through its declassified records and witness accounts. Promoting the second volume of his A History of USOs, he also described an underwater object encounter in the Mediterranean on May 1, 1975, in which, by his account, a large gray, pebble-shaped object rose from the sea, circled the carrier in view of at least 90 crew members and dove back into the water. Dolan's posts cite no government file for the 1975 event, which came several years after Blue Book closed. The 1952 Mainbrace photographs, described by Ruppelt and kept in copies among Grusinski's papers, remain the carrier's most fully recorded UFO report.