On June 5th, 1969 RC-135E 61-4137, known as Rivet Amber, departed Shemya for Eilson on a non-operational mission as Irene 92, with 19 people on board.
At 0936 local, approximately 40 minutes after departing Shemya, controllers at Elmendorf received a message that Irene 92 was experiencing an unknown
vibration, but the aircraft was under control. At 0937, Elmendorf asked for confirmation that they were not declaring an emergency, and received a
non-verbal response of a radio click, followed by heavy breathing and grunting. This was followed by two more radio clicks, the second of which
included the sentence, "crew go to oxygen". The radio clicks continued until 1022 local, but the last positive communications they had were the call
about the vibration.
Rivet Amber, previously known as Lisa Ann, was a unique aircraft. It was an RC-135E, and carried the most powerful airborne radar ever. The electrical
load and heat were so extreme that an additional engine mounted generator was mounted between the #2 engine and fuselage, and a radiator was installed
between #3 and the fuselage.
The radar was a 7 megawatt phased array system developed by Hughes. The radar weighed over 35,000 pounds, and was capable of tracking a soccer ball
sized object at 300 miles. It was so powerful that it was said that Soviet fighters w would stay well clear of Rivet Amber when intercepting her, out
of respect for the radar.
In 1969, Rivet Amber and Rivet Ball were flying out of Alaska together. In January, Rivet Ball was landing in poor weather, when they hydroplaned off
the runway, destroying the aircraft.
On 5 June, after they were unable to contact Rivet Amber, a massive search was launched. Aircraft from the bases in the area flew for two weeks,
carrying anyone that could see lightning, searching for any sign of the aircraft. At the end of two weeks, no sign of the aircraft was ever found. No
wreckage, no oil slick, nothing. The search was finally called off, and to this day no one knows what happened on that day.