Synopsis
On 30 August 2025 at 23:47 UTC, a serious incident occurred in the Mumbai oceanic control area approximately 197 nautical miles east of waypoint TOTOX on route P574. Two aircraft on reciprocal tracks—Turkish Airlines flight THY6380 (Airbus A330-223F, registration TC-JOO) and Flydubai flight FDB2JQ (Boeing 737 MAX 8, registration A6-FKR)—lost the required lateral and vertical separation. THY6380 was a cargo flight from Chennai to Istanbul cruising at FL340, while FDB2JQ was a passenger flight from Dubai to Calicut cruising at FL350. The incident was classified as an Airprox.
History of Flight
THY6380 departed Chennai at 21:42 UTC and was planned via route P574. The pilot-in-command (PIC) entered controlled rest after cruise briefing, leaving the first officer (FO) as pilot flying. Approximately one minute before the incident, the FO requested a climb to FL360 via Controller-Pilot Data Link Communications (CPDLC). The air traffic control (ATC) responded "Unable due to traffic." However, the FO misinterpreted a later blue message light as a clearance and initiated the climb.
At the same time, FDB2JQ, with its PIC also on controlled rest and the FO pilot flying, had deviated 2 nautical miles right of track due to turbulence. The aircraft was approximately 3 nautical miles ahead and 2 nautical miles laterally offset from THY6380, maintaining 1,000 feet vertical separation above.
As THY6380 climbed, the vertical and lateral separation was lost, triggering Traffic Advisory (TA) alerts on both aircraft. The respective PICs were awakened by the alerts. The PIC of THY6380, upon realizing the aircraft was climbing, queried the FO and verified via the DCDU recall that only the request message was displayed, not a clearance. He leveled off at FL350. The aircraft passed each other with less than the prescribed separation.
Final Determination
The investigation by the Aircraft Accident Investigation Bureau (AAIB) of India found that the probable cause of the serious incident was that the crew of THY6380 initiated a climb without obtaining ATC clearance.