What happened
On July 4, 2022, a serious incident involving a loss of separation occurred within the Muscat Flight Information Region (FIR). The event involved two aircraft: a Saudi Arabian Airlines Boeing 777, registration HZ-AK73, traveling from Hyderabad to Riyadh, and a Salam Air Airbus 320neo, registration A4O-OVH, traveling from Khartoum to Muscat.
At approximately 03:37 UTC, the air traffic controller (ATCO) instructed the Salam Air flight, OMS598, to descend to FL310 by the EGVAN reporting point. The crew of the Airbus 320neo manually entered FL310 into their Flight Management System (FMS) but did not engage the descent mode, choosing instead to maintain FL370 until their planned top of descent.
To prevent a conflict with the Saudi Arabian Boeing 777, which was maintaining FL340, the controller issued a new instruction at 03:39 UTC for OMS598 to descend to FL350 immediately. While the crew initially acknowledged this, they later initiated a descent toward their original target of FL310. This maneuver resulted in both aircraft experiencing TCAS Resolution Advisories (RA) as they breached separation minimums.