Factual Information
On 22 February 2018, Airblue flight ABQ 675, an Airbus A321-211 registered as AP-BMW, was operating a scheduled passenger flight from King Khalid International Airport, Riyadh, to Bacha Khan International Airport (BKIAP), Peshawar. BKIAP is a joint user airfield handling both civil and military traffic.
Sequence of Events
At 06:21 UTC, ABQ 675 contacted BKIAP approach maintaining FL160 and requested descent. The civil controller cleared the flight to FL150 and instructed it to join the hold overhead Peshawar. By 06:26 UTC, ABQ 675 reported joining the hold at 12,000 ft.
At 06:34 UTC, a Pakistan Air Force (PAF) formation of two F-7PG aircraft, call sign Benz Viper, was given traffic information about ABQ 675 holding at 12,000 ft. The PAF formation was subsequently cleared for take-off and climb to 10,000 ft. Traffic information about the departing military traffic was passed to and acknowledged by ABQ 675.
At 06:37 UTC, ABQ 675 reported a TCAS Resolution Advisory (RA) to the civil controller, with only 200–300 ft of vertical separation from the military traffic. The crew inquired whether the traffic information had been passed to the PAF formation, which was confirmed via the military controller.
At 06:38 UTC, ABQ 675 informed the controller that the PAF formation was also maintaining 12,000 ft. The military controller verified that the fighters were at 12,000 ft instead of the assigned 10,000 ft.
At 06:39 UTC, ABQ 675 climbed to FL140 in response to the TCAS RA. The military controller then advised the PAF formation to descend to 10,000 ft or climb to FL140; the formation chose to climb to FL140, the same level ABQ 675 was climbing to.
At 06:40 UTC, while passing through FL135, ABQ 675 reported a second TCAS RA due to the same PAF fighters climbing through its level. This occurred within three minutes of the first RA.
At 06:42 UTC, the PAF formation was re-cleared to FL160 by the military controller. Subsequently, ABQ 675 was cleared for an approach to Runway 35 and landed without further incident.
Findings
The investigation determined that the PAF formation climbed to 12,000 ft instead of the assigned altitude of 10,000 ft, despite having received traffic information about ABQ 675 prior to departure. No injuries or damage were reported to any aircraft. Weather was not a contributing factor.
Cause
The cause of the serious incident was that the PAF formation climbed to 12,000 ft instead of the assigned altitude of 10,000 ft despite traffic information which was passed prior to departure by ATC. A contributing factor was inadequate coordination between civil and military controllers.