What happened
On April 10, 1999, at 13:36 UTC, a British Airways flight, BAW1940, operating a Boeing 737, was on final approach to runway 05 at Geneva Airport. While established on the ILS at an altitude of 5,000 feet and approximately 10.5 nautical miles from the runway threshold, the flight crew observed a white glider with red markings flying directly above them at approximately 5,500 feet. The crew immediately notified Geneva Tower of the presence of the aircraft. Following the landing, the crew submitted an Air Traffic Incident Report (ATIR).
The investigation
An investigation by the Swiss Transportation Safety Investigation Board established that the incident occurred within Sector 1 of the Geneva Terminal Control Area (TMA). This specific airspace is classified as Class C. The investigation confirmed that the glider had entered this controlled airspace without obtaining prior authorization from air traffic services.
Technical analysis revealed that the glider was not transmitting a secondary surveillance radar signal (transponder), making it invisible to the controller's standard radar display. While the primary radar was only operational in an experimental capacity and was not available to controllers at the time, recorded primary radar tracks later confirmed the glider's presence. The investigation was unable to identify the pilot or the specific aircraft involved.
Findings
- The primary cause of the incident was the unauthorized entry of an unidentified glider into Class C airspace.
- The glider failed to establish contact with Geneva Tower prior to entering the controlled zone.
- The lack of a transponder signal prevented air traffic controllers from providing timely traffic information to the approaching heavy aircraft.
- The incident occurred under Visual Flight Rules (VFR) conditions, a common environment for glider operations in the region due to nearby airfields in France and Switzerland.
Safety action
Investigators noted that such incidents are frequent in the Geneva area due to the high density of glider operations at surrounding airfields. The report suggested that an information campaign targeting both Swiss and French glider pilots should be conducted to highlight the significant risks these incursions pose to commercial airliners carrying large numbers of passengers.