Ranking as the most talked about and invesitigated UFO incident since the late 1940's. The 'Roswell incident' as it is called, describes a UFO crash and retrieval that happened near the town of Roswell in July of 1947. After the recovery a group called Majestic 12 was formed to look into the UFO question and national security. These are supposedly the original members:

Rear Admiral Roscoe Hillenkoetter, first Director of Central Intelligence (1947-50). In 1960, he acknowledged there was a UFO cover-up.
Dr Vannever Bush, Chairman of the Joint Research and Development Board (1945-49). Advisor to the President, and key player in atomic bomb development.
James Forrestal, first US Secretary of Defence. In 1949, he allegedly had a mental breakdown and committed 'suicide'. Replaced by General Walter Bedell Smith. A book was written by Whitley Strieber called 'Majestic' which is allegedly Forrestal's actual diary describing the existance of UFO's.
Nathan Twining, Commander of Air Mat�riel Command at Wright Field and later, Chairman of the Joint Chiefs of Staff, the U.S.'s highest military position.
General Hoyt Vandenberg, Chief of Military Intelligence during World War 2 and second Director of Central Intelligence (1946-47).
Dr Detlev Bronk, biophysicist. Head of the National Academy of Science, and Chairman of the Medical Advisory Board of the Atomic Energy Committee.
Dr Jerome Hunsaker, renowned aircraft designer and Chairman of the National Advisory Committee on Aeronautics.
Rear Admiral Sidney Souers, first Director of Central Intelligence (1946). Appointed first Executive Secretary of National Security Council in 1947.
Gordon Gray, Assistant Secretary of the Army. Became the National Security advisor and Director of CIA's Psychological Strategy Board.
Dr Donald Menzel, Harvard professor of astrophysics, and debunker of UFOs. Held a Top Secret Ultra clearance and was adviser to several presidents. His presence in this group is unusual because he was an avid debunker.
Major General Robert Montague, head of the Special Weapons Project at the Atomic Energy Commission at Albuquerque, New Mexico.
Dr Lloyd Berkener, Executive Secretary of the Joint Research and development Board. Member of CIA-funded UFO committee in 1950s.