Incident
A NASA T-38 aircraft (registration N920NS) was inbound on a FINKS ONE arrival to Andrews Air Force Base with clearance to descend to 8,000 feet. In the same area, Pan Am Flight 140, an Airbus A310 (registration N806PA), was heading north at 7,000 feet after departing from Dulles International Airport (IAD).
The T-38 pilot descended through 8,000 feet and reported at 7,000 feet. The Washington (DCA) approach controller initially did not realize the T-38 was at the wrong altitude. Shortly thereafter, the conflict alert system alarmed, and the DCA controller issued a traffic advisory. The T-38 pilot immediately climbed to 8,000 feet.
Before the climb, radar data indicated that the Airbus and T-38 passed each other with 711 feet of lateral separation and 100 feet of vertical separation. The Airbus pilot stated that he saw the T-38 pass ahead from left to right.
Air Traffic Control Actions
The T-38 was handled by Washington (DCA) approach control, while the Airbus was handled by Dulles (IAD) approach control. The IAD controller noticed traffic for the Airbus but did not issue a traffic advisory. Additionally, the IAD controller stated that his conflict alert system did not alarm; however, computer data indicated that the alarm had operated.
Outcome
The aircraft did not collide. No injuries or damage were reported in the source.