History of the Flight
On 10 February 2024 at 23:55 UTC, a serious incident occurred in the Muscat Flight Information Region (FIR) involving two commercial aircraft: Etihad Airways flight ETD455, a Boeing 777-3FXER registered as A6-ETP, and Qatar Airways flight QTR71N, an Airbus A320-232 registered as A7-AHP.
At the time of the incident, aircraft ETD455 was maintaining flight level (FL) 340 while flying westbound on bidirectional Airway P570 between waypoints KITAL and GOLNI. Aircraft QTR71N was flying eastbound at FL350 on the same airway. The Middle Sector Air Traffic Controller (ATCO) cleared QTR71N to descend from FL350 to FL330, which required it to pass through ETD455's altitude of FL340.
At 23:55:39 UTC, as QTR71N was descending through FL341 at a rate of 400 feet per minute (FPM), and ETD455 was maintaining FL340, the two aircraft were on a head-on collision course with a closing distance of 7.38 nautical miles. The Traffic Collision Avoidance System (TCAS) on both aircraft generated a Resolution Advisory (RA) prompting immediate evasive maneuvers. Both flight crews reported the TCAS RA and executed the avoidance maneuvers before the controller could issue instructions. The controller subsequently instructed both aircraft to turn right 50 degrees, but the crews had already responded to the TCAS RA.
After the conflict was resolved, ETD455 returned to FL340, and both flights continued without further incident. No injuries to persons or damage to aircraft were reported. The investigation noted that the controller's clearance to QTR71N to descend through ETD455's occupied altitude led to the loss of standard separation.
Aircraft Information
Etihad Airways flight ETD455 was operated using a Boeing 777-3FXER, registration A6-ETP. Qatar Airways flight QTR71N was operated using an Airbus A320-232, registration A7-AHP. Both aircraft were equipped with TCAS and were operating under Instrument Flight Rules (IFR) in Reduced Vertical Separation Minima (RVSM) airspace.
Location and Timing
The incident occurred in the Muscat FIR at coordinates 20°32'58.39"N 059°59'05.57"E. The time of the closest proximity was 23:55:39 UTC. The local time in Oman (UTC+4) was 03:55 on 11 February 2024.
Investigation
The Oman Transport Safety Bureau (OTSB) conducted the investigation in accordance with national and international regulations. The investigation focused on the actions of the air traffic controller and the flight crews, as well as the performance of the TCAS system. No causal or contributing factors were explicitly stated in the released summary, but the sequence of events indicates that the descent clearance created the conflict.