What happened
On the day of the event, an FAA Beech 300, operating as FLC72, was flying southeast on airway J79 at flight level 260. Simultaneously, TWA Flight 393 was traveling south on airway J45 at flight level 310. Both aircraft were operating under instrument flight rules (IFR) and were being controlled by the R5CO controller at Jacksonville ARTCC.
The controller was managing a high volume of other traffic at the time. FLC72 requested a descent, but the instruction was delayed while the controller coordinated traffic with another controller. During this delay, Flight 393 was cleared to descend to flight level 240. Approximately 90 seconds later, FLC72 received instructions to fly a heading of 195 degrees and to descend to and maintain 16,000 feet. Although the crew of FLC72 acknowledged the instruction, the aircraft did not descend in a timely manner, and the controller did not identify this deviation.
As a result, FLC72 and Flight 393 converged, resulting in a horizontal separation of approximately 0.8 miles at the same altitude.
Findings
The investigation determined that the close proximity occurred while the captain of FLC72 allowed the first officer to leave the cockpit to permit another FAA employee to occupy the co-pilot's seat. The captain reported that he may have become distracted while briefing the visiting employee.