FlightFollowerNear Collision | UNIDENTIFIED Military Surveillance Aircraft Disrupts Air Traffic
The Warning Came Minutes After Takeoff
On December 12, 2014, a Bombardier CRJ-200 operated by Cimber for SAS departed Copenhagen for Poznan, Poland. Only minutes into the flight, Swedish civil controllers became concerned about unidentified military traffic near the passenger aircraft's route.
Accident Facts
- Date
- 12 December 2014
- Flight
- Cimber/SAS Flight SK1755
- Aircraft
- Bombardier CRJ-200
- Location
- South of Sweden, over the Baltic
- Outcome
- No collision; unidentified military aircraft avoided, flight continued to Poznan
The Russian military aircraft was flying with its transponder switched off, making it invisible to normal civilian surveillance systems. Swedish military surveillance detected the aircraft and passed the information to civil ATC.
The passenger crew was first cleared to climb higher. That clearance was then withdrawn when controllers recognized the conflict. The aircraft was told to stop climbing and later instructed to turn right. The CRJ passed behind the military aircraft rather than continuing into the developing conflict.
The Civilian Radar Picture Was Missing a Key Target
The most important technical feature was the military aircraft's lack of a transponder and normal ATC coordination. Swedish military surveillance detected it, but civil controllers did not initially have the same identification picture.
That created a classic information asymmetry. One surveillance system knew that an aircraft was present; another part of the air-traffic system had to work with incomplete information.
The passenger aircraft's crew therefore received a warning about traffic they could not necessarily identify visually. Their response depended on following ATC instructions and trusting the information being provided.
The Incident Was Serious — but the Accounts Were Not Identical
Swedish authorities described the situation as dangerous, while the Russian Defense Ministry later disputed that there had been a collision risk and said the military aircraft remained at a safe distance.
That disagreement should remain visible . The event itself is not disputed: a Russian military aircraft was operating near the civilian route, Swedish authorities warned the passenger aircraft and the passenger flight changed its climb and heading.
What is disputed is the degree of actual collision risk. The safest reporting therefore describes it as a near-collision or serious separation event based on the Swedish account, while noting the Russian denial.
The ATC Intervention Worked
The strongest safety point is what happened after the warning reached the controller. The passenger aircraft stopped climbing and turned away. According to contemporary reporting, it passed behind the Russian aircraft.
That response converted a potentially dangerous geometry into a controlled separation maneuver. The event demonstrates why surveillance cooperation matters: military detection provided the information that civilian controllers needed to act before the two aircraft reached the same space.
The Passenger Crew Was Given a New Picture of the Airspace in Real Time
The sequence shows how quickly an ATC clearance can change when a previously unidentified target is detected. SK1755 was cleared toward 25,000 feet and only minutes later was told to stop climbing.
The Swedish military surveillance system was critical because the Russian aircraft was not visible to civilian controllers in the normal way. The military warning allowed civil ATC to issue an avoidance instruction before the aircraft reached the same point.
The encounter therefore demonstrates the value of integrating military and civil surveillance when unidentified traffic operates near civil routes.
Contemporary Swedish reporting records that the crew was told to “stop the climb at 22,000 feet.”
Conclusion
SK1755's encounter over the Baltic was a conflict created by incomplete traffic visibility. A Russian military aircraft operated without a transponder, Swedish military surveillance detected it and civil ATC then redirected the passenger aircraft.
The two governments later differed over whether a true collision risk existed. The safety lesson does not depend on resolving that political dispute: when an unidentified aircraft is near a civil route, rapid information sharing and conservative ATC action can keep a serious encounter from becoming an accident.