Background
During a familiarization training session at Boston Air Route Traffic Control Center (ARTCC), a full performance level (FPL) controller was training another FPL controller in Sector 31. The sector had recently been transferred from New York ARTCC and was considered complex and busy.
Incident
At a busy period after traffic had peaked, the controllers were focused on a potential conflict between two aircraft. Meanwhile, Eastern Airlines Flight 380 (EA380), a Boeing 727, began converging with a third aircraft, MAC 67947, a United States Air Force C-141. The conflict alert system activated, prompting controllers to issue a turn to avoid convergence. Despite this, the two aircraft passed within half a mile of each other at the same altitude assignment.
Details
EA380 had been assigned an abnormally low altitude of FL230 for its routing. The conflict occurred when EA380 turned in response to an ARTCC clearance.