Overview
On January 20, 2011, at approximately 2235 Eastern Standard Time, a near mid-air collision (NMAC) occurred between American Airlines flight 951 (AAL951), a Boeing 777-200, and a flight of two US Air Force C-17s operating as THUG11. The incident took place within New York Air Traffic Control Center (ZNY) Class A airspace.
Flight Details
AAL951 was a regularly scheduled passenger flight under 14 CFR Part 121, operating from John F. Kennedy International Airport (JFK) to São Paulo, Brazil. THUG11, a two-aircraft formation under 14 CFR Part 91, had departed aerial refueling track AR777 and was en route to Joint Base McGuire-Dix-Lakehurst (WRI), New Jersey. At the time of the incident, AAL951 was climbing to FL220 in a southeast-bound direction, while THUG11 was descending from FL250 to FL220 on a northwest-bound heading. Both aircraft were assigned the same altitude, FL220, due to a misunderstanding between air traffic controllers.
Air Traffic Control
The two aircraft were managed by different controllers within ZNY Sector 86. The R86 controller was handling THUG11, while the R66 controller was responsible for AAL951. At about 2228, THUG11, along with a KC-10 tanker (TEAM48), contacted the R86 controller for clearance back to WRI. The controller instructed THUG11 to turn right to heading 030. Shortly after, AAL951 checked in with the R66 controller and was cleared direct to the KINGG intersection and to climb to FL230.
At 2232, the R86 controller cleared THUG11 to descend to 10,000 feet via COYLE. At 2233, the R86 controller attempted to contact AAL951 but received no response. At 2234:01, the R86 controller instructed THUG11 to maintain FL210. Meanwhile, the R66 controller was occupied with a flight plan read-back from Continental Airlines flight 31 (COA31), which took approximately 57 seconds. Coordination between controllers was further hampered when a request to stop AAL951 at FL200 was not acted upon due to the R66 controller's focus on COA31.
At 2234:38, the R86 controller directed THUG11 to turn right to 020 for traffic. At 2234:58, he instructed THUG11 to maintain FL220. At 2235:01, the R66 controller instructed AAL951 to turn 30 degrees right and maintain FL220. Subsequently, at 2235:35, the R66 controller advised AAL951 to turn left at its discretion due to traffic.
TCAS Events
The ZNY radar system generated a conflict alert (CA) when the aircraft were about 88 nautical miles east of New York City. Concurrently, AAL951 received an initial Traffic Alert and Collision Avoidance System (TCAS) resolution advisory (RA) to descend, followed by a second RA increasing the descent rate, and a third RA reversing to a climb. THUG11 operated TCAS in "TA only" mode per Air Force instructions, so its crew received only traffic advisories (TA) and did not deviate from ATC instructions.
Aftermath
Radar data showed the aircraft passed within approximately 0.38 nautical miles laterally and zero feet vertically. The crew of THUG11 reported coming within about 2,000 feet of the traffic. AAL951's pilot reported the encounter negatively. The R66 controller apologized, stating he was not working the other aircraft. The second C-17 in formation (THUG12) was about 4,000 feet in trail and offset 500 feet right, but was not directly involved in the NMAC.