What happened
On July 7, 1998, at 16:14 UTC, a British Airways flight, BAW730, operating a Boeing 757 from London Heathrow to Geneva, experienced a near-collision while descending toward the Geneva terminal area. While flying under radar control from Geneva Approach, the aircraft was descending through flight level 097 when the crew encountered an unidentified aircraft at a very close distance. The pilot immediately initiated an avoidance maneuver by climbing to flight level 100. The crew reported seeing a white Pilatus-type glider approximately 1 nautical mile ahead and 200 feet below the aircraft.
The investigation
The investigation established that the encounter occurred in Class E airspace, north-northwest of the SPR/VOR, outside the Geneva terminal control region. At the time of the incident, weather conditions were favorable for visual flight rules (VMC) with visibility exceeding 10 kilometers. The investigation found that the unidentified glider was not detectable by primary or secondary radar, meaning the air traffic controller could not alert the crew to its presence. While the Boeing 757 was operating under instrument flight rules (IFR), the unidentified aircraft was operating under visual flight rules (VFR) and, because it was in Class E airspace, was not required to communicate on the approach frequency.
Findings
- The primary cause of the incident was the presence of an uncontrolled VFR aircraft within Class E airspace during the approach of an IFR airliner.
- The unidentified glider was invisible to radar services, preventing proactive separation by the controller.
- The flight path of BAW730 had transitioned through various airspace classes, including French airspace, before entering Swiss airspace at flight level 103.
Safety action
To prevent similar occurrences, it is recommended that aircraft operating under instrument flight rules (IFR) avoid traversing Class E airspace.