What happened
On 6 March 2005, a Boeing 737-800, registration G-XLAA, operating from London Gatwick to Chambéry, and a Falcon 2000, registration LX-SVW, flying from Moscow-Vnukovia to Geneva, experienced a serious airprox incident near the CBY VOR in the Geneva TMA.
While the Boeing 737-800 was being vectored toward Chambéry, the Geneva Approach controller cleared the aircraft to join the CBY holding pattern at flight level 080. Upon being transferred to Chambéry Approach, the pilot was instructed to join the VIRIE holding pattern instead. The pilot failed to correctly read back this change in the specific holding pattern.
As the Boeing 737-800 initiated a left turn—the shortest route to the VIRIE pattern via its flight management system—it entered the Geneva TMA. This movement placed it on a converging path with the Falcon 2000, which was on approach to Geneva. The Chambéry controller observed the conflict and ordered an immediate right turn and rapid climb. Simultaneously, the Geneva controller issued emergency instructions to the Falcon 2000 to descend rapidly to avoid the intruding aircraft. Both crews experienced a TCAS traffic advisory (TA) as the aircraft closed to a lateral separation of approximately 2.5 NM and an altitude difference of only 100 ft.
The investigation
The investigation examined the communications and coordination between Geneva and Chambéry Approach units. Investigators found that the telephone coordination between the two controllers failed to prevent the convergence. Specifically, the Geneva controller issued an incorrect clearance regarding the holding pattern, and the arrival route prescribed by the Letter of Hold Agreement was not being followed by either unit.
Furthermore, the investigation analyzed the pilot's readback and the controller's failure to correct the omission of the specific holding pattern name. The investigation also reviewed the flight management system (FMS) inputs, which led the Boeing 737-800 to execute a left turn toward the VIRIE pattern.