Project SIGN was the first major classified report on the subject of unidentified flying objects to be issued by the Air Force. Some portions are rather dry and bureaucratic, while other areas of this report are quite frank and even surprising in their candor - and in their consideration of UFOs as someone else's "spaceships." The original version runs 44 pages in total. Here are pages 8,9,10, dealing with "Round Objects (Spherical-and Balloon-Shaped Objects)"
References:
Title:
Project "SIGN"
To:
Selected individuals and agencies
Authors:
Headquarters, Air Materiel Command (AMC), Wright-Patterson Air Force Base, Dayton OH
