High-altitude testing of the U-2 soon led to an unexpected side effect-a tremendous increase in reports of unidentified flying objects (UFOs). In the mid1950s, most commercial airliners flew at altitudes between 10,000 and 20,000 feet and military aircraft like the B-47s operated at altitudes below 40,000 feet. Consequently, once U-2s started flying at altitudes above 60,000 feet, air- traffic controllers began receiving increasing numbers of UFO reports. Such reports were most prevalent in the early evening hours from pilots of airliners flying from east to west. When the sun dropped below the horizon of an airliner flying at 20,000 feet, the plane was in darkness. But, if a U-2 was airborne in the vicinity of the airliner at the same time, its horizon from an altitude of 60,000 feet was considerably more distant, and, being so high in the sky, its silver wings would catch and reflect the rays of the sun and appear to the airliner pilot, 40,000 feet below, to be fiery objects. Even du