Incident Overview
On August 15, 2014, about 2133 Alaska daylight time, a loss of separation occurred between American Airlines flight 183 (AAL183), a Boeing 777-200 en route to Shanghai Pudong International Airport, and China Airlines flight 5254 (CAL5254), a Boeing 747-400 en route to Ted Stevens Anchorage International Airport. The incident took place near Shemya, Alaska. Both flight crews responded to resolution advisories from their onboard Traffic Alerting and Collision Avoidance System (TCAS). The Federal Aviation Administration (FAA) estimated the minimum separation between the two aircraft was 1.04 miles and 900 feet. There was no damage to either aircraft and no injuries to passengers or crew.
Sequence of Events
At 2113:08, sector 11R received a controller–pilot data link communication (CPDLC) message from CAL5254 requesting a climb from flight level (FL) 360 to FL 370. CAL5254 was established eastbound on R-590. Sector 11R responded via CPDLC to "climb to FL370 by 0520" (2120 local time).
At 2116:08, sector 11R received a request from AAL183 to climb from FL360 to FL370. AAL183 was westbound on the Pacific Organized Track System (PACOTS) track "E" from AMOND direct to OPAKE to join the northern Pacific R580. At 2118:43, sector 11R used the time passing tool from the Advanced Technologies and Oceanic Procedures (ATOP) Ocean 21 system and determined separation between Korean Airlines (KAL) 035 and AAL183 would be 15.9 nautical miles at 2126 local.
At 2118:52, sector 11R instructed AAL183 to "[At] time 0530 (2130) climb to FL370." At 2119:10, AAL183 acknowledged the climb clearance via CPDLC.
At 2131:55, a radar-based conflict alert activated between CAL5254 and AAL183. The sector 11R air traffic controller used the time passing tool and determined the lateral separation between CAL5254 and AAL183 would be 0.80 nautical miles at 2133.
At 2132:18, the sector 11R air traffic controller made a blind transmission attempting to contact AAL183; there was no reply. At 2132:25, the controller made a blind transmission attempting to contact CAL5254; again, there was no reply.
At 2132:29, CAL5254 made a transmission that they were responding to a TCAS RA and climbing. At 2132:44, the pilot advised the RA was complete and they were descending back to FL370.
At 2133:26, AAL183 contacted sector 11R and advised "yeah we had a uh we requested three seven oh, we got a CPDLC message said that at oh five thirty to climb to three seven oh we did that and ah we just got an RA with another aircraft." The sector 11R air traffic controller replied, "American one eighty three roger, yup, that clearance should have been delayed."
Aftermath
No additional details were provided in the source regarding subsequent actions or investigations. The incident was documented in the ATC Group Chairman's factual report.