Smyrna, DelawareMay 1961

In May 1961, a resident of Smyrna, Delaware, reported seeing a bright object that flashed or flickered low on the horizon. The observer had written to the President of the United States in late May describing the sighting. On June 16, the U.S. Air Force's Project Blue Book office responded to the report.

The Air Force investigator, Major William Coleman, concluded that the sighting most likely matched a radiosonde balloon launched from Sterling, Virginia. A radiosonde is a weather balloon carrying a radio transmitter used to measure temperature and wind conditions at high altitudes. When such balloons eventually burst at extreme altitude due to expansion and low temperature, the fragments fall at high speed in multiple directions. The Air Force noted that the object's brightness could have come from sunlight reflecting off the balloon, which in some cases can appear brighter than the planet Venus.

Coleman suggested the observer might see more such balloons in the future if they looked between bearings 230 and 300 degrees (roughly southwest to northwest) near the horizon, between 7:45 p.m. and 9:00 p.m. local time. He also noted that Dover Air Force Base might be launching similar balloons, and recommended checking with their information officer to confirm launch schedules. The observer was encouraged to report any future sightings that did not fit this pattern using an enclosed questionnaire.

The Air Force's evaluation for this case was listed as "unknown," although the file indicates the investigator believed the sighting most likely involved a weather balloon. This 15-page case file is reproduced below as held by the National Archives.