James Louis Warsher and a friend were driving across the Anderson Memorial Bridge in Harvard Square when they noticed a dull gray elliptical vessel tinted with muted yellow light descending from the sky. It was around 8:30 p.m. on Sept. 9, 1964, and the two were among 11 Bostonians who reported UFO sightings that night. Air Force investigators said the object was just an advertising plane. They confirmed it by cross-checking the aircraft's flight plan. But the Air Force's official explanation ... couldn't answer one issue: When Warsher and his friend saw the UFO, it was flying within sight of the same plane the investigators purported it to be. This story is one of more than 12,000 chronicled by Project Blue Book, the Air Force's UFO investigation program that ran from 1947 to 1969. The once-classified files ... have become more accessible to the general public in recent years through Fold3, a commercial database of government and military documents. Readers can sort the files by date, state, and when they were added to the website. The collection reveals how the nation's military bureaucracy painstakingly documented what amounted to a cultural phenomenon of the Cold War. Even though the Air Force deemed only a small portion of the reports unexplainable, UFO researcher Stanton Friedman believes Project Blue Book barely scratches the surface of American UFO investigations. Friedman claims the Air Force has gotten away with carefully worded misrepresentation," of its interest in the aircraft.