A serious near-miss involving a Turkish Airlines cargo flight and a Flydubai passenger flight over the Arabian Sea last year occurred because the Turkish Airlines co-pilot initiated an unauthorised climb that breached the required vertical separation between the two aircraft, according to the final report recently released by the Aircraft Accident Investigation Bureau (AAIB).
Incident Overview
The incident took place on August 30 over the north-east Arabian Sea when the Turkish Airlines cargo flight, operating from Chennai to Istanbul, violated vertical separation and came dangerously close to a Flydubai passenger flight travelling from Dubai to Calicut. The Turkish Airlines flight (THY6380) was cruising at 34,000 feet, while the Flydubai aircraft (FDB2JQ) was flying 1,000 feet directly above at 35,000 feet, heading in the opposite direction on the same oceanic route, P574. Both captains were on controlled rest at the time, leaving their respective first officers in charge.
Communication Breakdown
The Turkish Airlines first officer had earlier requested a climb to 36,000 feet through the Controller Pilot Data Link Communications (CPDLC) system, a digital text-based communication tool used between pilots and air traffic controllers, especially over oceanic airspace where radio coverage is limited. The Mumbai air traffic control (ATC) declined the request, responding with “Unable due to traffic.” However, the ATC reply was sent without a required reference number linking it to the original request. As a result, the aircraft’s onboard system did not register it as a formal response. After 7 minutes and 30 seconds, the system automatically generated a reminder displaying the original climb request on the cockpit screen.
Critical Misinterpretation
When the reminder appeared, accompanied by a flashing blue attention light, the first officer misinterpreted it as a fresh clearance to climb and initiated the manoeuvre without cross-checking with his captain or ATC. Within seconds, both aircraft were closing on each other with insufficient separation, triggering collision avoidance alarms in both cockpits. The report noted: “As per the crew statement of both the aircraft Capts were awakened from controlled rest by the sound of Traffic Advisory ‘TRAFFIC TRAFFIC’.”
Probable Cause and Contributory Factors
The AAIB determined that the Turkish co-pilot’s failure to verify the CPDLC message and the absence of the required two-pilot cross-check before executing a significant altitude change was the probable cause of the incident. Contributory factors included the ATC’s omission of the message reference number and a gap in crew knowledge about how cockpit reminder messages function. The incident highlights critical issues in communication protocols and crew resource management.
