What happened
On April 17, 1998, a Boeing 737-20 and a Boeing 747-400 experienced a near mid-air collision in the airspace west of the KOLJA intersection within the Malmö FIR. The Air France flight, operating as F-GBYC, was cruising at 35,000 feet when the air traffic controller at position R 7 decided to descend the aircraft to 31,000 feet. This maneuver was intended to allow a faster-moving aircraft to overtake without delay.
However, the controller failed to identify that a British Airways flight, G-BNLK, was traveling on an intersecting course at 33,000 feet. During the descent, the crew of F-GBYC observed the oncoming heavy jet and performed evasive maneuvers to the right. The aircraft passed each other with a lateral separation of less than 1 nautical mile and a vertical separation of only approximately 300 feet. The crew of G-BNLK also performed evasive action and subsequently received a TCAS warning.
The investigation
An investigation by the Swedish Board of Accident Investigation (SHK) focused on the air traffic control environment at the time of the incident. The controller at position R 7 was simultaneously instructing a student, which increased the complexity of the task. At the time of the event, the controller was managing a high volume of traffic following a sudden influx of flight strips.
Investigators also examined the possibility of a radar mosaic effect, where the intersection of two radar stations can cause an aircraft echo to disappear temporarily. While the controller noted that this might have obscured the incoming flight during the conflict search, the investigation primarily focused on the operational pressures present in the sector.