Loss of Separation Between Two Aircraft in Warsaw FIR

What happened

On May 3, 2015, an air traffic management incident occurred within the Warsaw Flight Information Region (FIR EPWW) near the ALUKA navigational point. Two aircraft, a Boeing 737-800 (operating flight UUDD EDDT) and a Boeing 77W (operating flight VTBS EHAM), were traveling along the same airway. The trailing aircraft was traveling approximately 50 knots faster than the leading aircraft. During the encounter, the minimum separation between the two aircraft decreased to 6.5 NM horizontally and 500 ft vertically, failing to meet the required minimum separation standards of 7 NM horizontally or 1000 ft vertically.

The investigation

The investigation examined the actions of the air traffic controller (ACS) and the coordination of the aircraft. It was established that the controller was on their third shift following two days of leave. While the number of open sectors and traffic density were within moderate limits, the investigation focused on the failure to implement corrective maneuvers. The controller held all valid licenses and medical certifications, having completed refresher training in late 2013.

Findings

• The aircraft were traveling on the same route, with the following aircraft maintaining a significant speed advantage of approximately 50 knots.
• The controller failed to implement parallel or divergent headings (such as coordinating the Boeing 77W via the NORKU or ARTIP points) to maintain separation.
• The controller did not issue a descent speed restriction to intercept FL290, despite decreasing separation measurements and automated