[ILLEGIBLE], [ILLEGIBLE] 1948 - Incident Number: 215Circa 1948

On December 3, 1948, at 2015 hours (8:15 p.m.) Pacific Standard Time, the control tower operator at Fairfield-Suisun Air Force Base in California saw a bright white light moving rapidly through the sky. The object first appeared about two miles north of the tower at an altitude between 500 and 1,000 feet, climbing steadily at a speed of more than 400 miles per hour.

As the object drew closer to the base, its behavior changed dramatically. When it reached an altitude of roughly 1,500 feet, it slowed to about 200 miles per hour and began a slight undulating or bouncing motion. Moments later, the object executed an almost vertical climb to about 2,000 feet, leveled off briefly, then shot upward again at high speed until it disappeared from sight at an estimated 20,000 feet. The entire sighting lasted only 25 seconds.

The observer described the object as a round light roughly 30 inches in diameter, comparable in brightness to one of the base's high-intensity runway lights. He was confident it was not an aircraft navigation light. The night was clear, visibility was good, and no sound was heard. When viewed through binoculars, the object appeared as a circular light so bright that it masked any detail of the object's shape or structure.

Air Force meteorologists and analysts ruled out conventional explanations. A weather balloon had been released 45 to 75 minutes before the sighting but was lost from view 10 minutes after release. Wind conditions at altitude were very strong, 60 to 70 miles per hour from the east, which would have prevented any balloon from moving in the direction the object traveled. The Air Force's Aero Medical Command concluded there was no logical explanation for the incident based on available evidence. The full case file, comprising 30 pages, is reproduced below as held by the National Archives.