RB-47 intercept by unidentified object — South-central United States

On July 17, 1957, a USAF RB-47 electronic reconnaissance aircraft was trailed over the south-central United States by an unknown object detected simultaneously by airborne electronic intelligence equipment (pulsed microwave emissions), visual observation by crew, and the 'Utah' ground radar near Dallas. The object mirrored the RB-47's speed changes while maintaining a constant 18 km separation. A red light was visually observed by the pilot below and at 2 o'clock. The object appeared and disappeared from all detection systems simultaneously on multiple occasions. The Condon Commission classified the case as unresolved.

“Commander Chase perceived a large red light, which he estimated was moving 1500 m below the aircraft at approximately '2 o'clock'... Utah informed him that the object was mirroring his movements, all the while maintaining a constant distance of 18 km.”

Source is COMETA 1999 analytical report, summarizing MacDonald's 1971 investigation and the DIA/Blue Book record. Six crew members were interviewed by MacDonald in 1969. Classified as unresolved by Condon Commission.