Page:NTSB Aircraft Accident Report, United Airlines Flight 389.pdf/7

 it correctly. This was the last communication received from the flight and ended at 2120.03.

The USAF Air Defense Command radar system and the SAGE computer were monitoring and recording certain high altitude tracks by position, altitude, time, heading, and ground speed. The SAGE data were reviewed and showed two tracks in the area of concern at the time UAL 389 was approaching O'Hare. The first track, identified by the computer as track A039, began at 0157.8Z (2057:48) at a point approximately 17 nautical miles west of the Salem, Michigan VORTAC (83°58' West - 42°17' North) and was dropped by the computer at 87°10' West - 42°17' North at 0217.3Z (2117:24). The second track, identified as K047, was initiated at 0218.6Z (2118:36) at 87°23' West - 42°15' North, and dropped at 0222.8Z (2222:48) at 87°52' West - 42°15' North. There was no other high altitude traffic observed by ARTCC or SAGE in the area of concern at the time UAL 389 passed through it. The track over the ground, ground speed and positions observed by SAGE were compatible with the intended flight path of UAL 389, and within the normal operating envelope of the B-727. In addition to the tracking