The so-called green fireballs of 1948-1949
Under the recent law making most government records available to the public, B.S. Maccabee obtained the FBI's UFO file. His analyses of this file have been serialized in the APRO Bulletin. One of the most unsettling revelations concerns the FBI data on the notorious "green fireballs" of the 1948-1949 era. According to the verbatim transcript of the FBI record, dated January 31, 1949, File No. 5: November 1978
Briefly, the "fireballs" were a brilliant green, sometimes beginning and ending with red or orange flashes. The objects travelled mainly on an east-west line at an average speed of 27,000 miles per hour. They seemed to pass over in level flight at altitudes of six to ten miles. On two occasions vertical changes of course were noted. Size was about one-fourth the diameter of the full moon. Multiple fireballs appeared in two instances. No sound was ever noted. No debris was ever discovered.
(Maccabee, Bruce S.; "UFO Related Information from the FBI File," APRO Bulletin, 7, March 1978.)