Incident Overview
On 20 April 2017 at 06:58 UTC, an incident occurred 13 NM north of Palma de Mallorca Airport (Illes Balears, Spain) at an altitude of 12,000 ft. The incident involved a Boeing 737-800, registration EC-JBK, operated by Air Europa, and a Cessna Citation C510, registration EC-LCX, operated by Caladero Aviation. The Boeing was on approach to Palma de Mallorca from Barcelona, while the Cessna was climbing after departure from the same airport. No injuries were reported among the 168 persons on board the Boeing or the 2 persons on board the Cessna.
Sequence of Events
The Boeing 737 was instructed to maintain FL120 and was stabilized at that level at 06:56:30. The Cessna Citation had been instructed by the Palma ACC sector F1X controller to stop climbing at FL110. At 06:55:21, the crew of the Cessna acknowledged the instruction but read back FL120. The controller did not correct this misread. The Cessna continued climbing and stabilized at FL120 at 06:57:45. At that moment, the horizontal distance between the two aircraft, which were on a collision course, was 2.5 NM.
Detection and Avoidance
Both crews reported having the other aircraft in sight. The ACAS (Airborne Collision Avoidance System) on each aircraft issued a Traffic Advisory (TA). No Resolution Advisory (RA) was generated. The aircraft did not collide, and no evasive maneuvers were necessary. No damage occurred.
Communication and Radar Data
Radar data confirmed the positions and altitudes. The controller in sector F1X was managing the traffic. The miscommunication regarding the cleared flight level was not corrected by the controller. The incident was classified as a loss of separation.