What happened
On 25 November 2014, at approximately 08:20 UTC, a serious runway incursion occurred at Paris-Charles de Gaulle airport involving two Airbus aircraft. The first aircraft, a Bulgaria Air Airbus A319-112 (registration LZ-FBB), had recently vacated runway 08R and was taxiing toward the terminal. Simultaneously, a Freebird Airlines Airbus A302-232 (registration TC-FBJ) was performing its takeoff roll on runway 08L.
As the Bulgaria Air crew approached the intersection of taxiway S6 and runway 08L, the air traffic controller instructed them to "keep on taxiing" to manage traffic priorities. The crew of LZ-FBB interpreted this instruction as a clearance to cross the runway. Consequently, the aircraft entered runway 08L. At that moment, the Freebird Airlines aircraft was at an airspeed of approximately 139 knots and roughly 1,500 meters from the intersection. The collision alarm (RIMCAS) was triggered as the LZ-FBB entered the runway, and the TC-FBJ crew reported flying over the taxiing aircraft at a height of approximately 100 feet.
The investigation
The BEA examined radio recordings, radar data, and flight data recorders from both aircraft. The investigation focused on the air traffic control environment, noting that the local controller was managing a high workload due to dense inbound traffic and reduced separation between arriving aircraft.
Investigators also reviewed the communication between the controller and the various crews. While the controller had used English for the Bulgaria Air crew, subsequent instructions regarding a third aircraft (an Air France flight) were conducted in French. The investigation also looked into the physical configuration of the Paris-CDG runways, specifically how the elevation difference between the runway and taxiway intersections can impede a pilot's ability to see departing aircraft.