Incident Overview
On an unspecified date, a Canadian Pacific McDonnell Douglas DC-10 (Flight 3, registration CG-CPJ) and a Reeve Aleutian Boeing 727 (Flight 724, registration N832) came within approximately half a mile of each other at Flight Level 290 over the Bearing Sea. Both aircraft had been cleared to fly at FL 290 on different airways that intersected at the PICUM intersection.
Sequence of Events
The DC-10 crew observed the Boeing 727, but the 727 crew did not see the DC-10. The PICUM intersection was located beyond normal radio and radar range of air traffic control (ATC) controllers. Two on-duty controllers had initially combined sectors 10 and 11 before dividing the airspace into a north-south configuration, a practice contrary to standard operating procedures (SOP). The incident occurred during a busy period, and a supervisor was assisting one of the two controllers.
Controller Actions
The controller responsible for Flight 3 cleared it to descend from FL 330 to FL 290. According to this controller, he informed the other controller to stop Flight 724 at FL 280, as Flight 724 was climbing from a lower altitude. The controller handling Flight 724 stated that he was unaware of any aircraft at FL 290 when he cleared Flight 724 to that altitude.
Aircraft Information
The DC-10 was operated by Canadian Pacific, while the Boeing 727 was operated by Reeve Aleutian. Both aircraft were flying in nearly opposite directions at the same altitude when the near midair collision occurred at the airway crossing.