What happened
Between December 13 and December 15, 2000, a series of eight airprox events occurred in the airspace over the lower Tyrrhenian Sea. The incidents involved several commercial flights, including Alitalia, Air Europe, and Meridiana, all encountering unidentified traffic, believed to be military in nature, within controlled Class A airspace.
On December 13, an MD-82, registration I-DAWY, operating flight AZA 1850 from Naples to Palermo, experienced a TCAS Resolution Advisory (RA) during its climb. The pilot halted the climb at 22,000 feet to maintain separation from a military aircraft at 24,000 feet.
On December 14, flight AZA 1766, an MD-80 with registration I-DATK, flying from Palermo to Milan Malpensa, detected traffic via TCAS at approximately 15 NM and performed a precautionary 10-degree course change. On the same day, flight AZA 1851, an MD-80 registered I-DANH, flying from Palermo to Naples, encountered two unidentified aircraft flying in formation. The distance between the civilian aircraft and the unknown traffic closed to 4.4 NM, with a vertical separation of 800 feet. Additionally, flight AZA 1809, an MD-80 registered I-DAVD, encountered intense unidentified traffic while cruising from Palermo to Bologna.
On December 15, further encounters were reported involving flights AZA 1794, AZA 1798, AEL 622, and ISS 698, all involving unidentified traffic in the same geographic area.
The investigation
The ANSV launched a technical investigation following reports from Alitalia regarding unidentified traffic interfering with flight routes. The investigation involved reviewing air safety reports, radar tracks, and radio communications from ENAV (the Italian air traffic services provider). The inquiry also involved coordination with the Italian Military Prosecutor's Office, the Italian Air Force, and the United States Embassy in Rome.
Investigators established that the unidentified aircraft were likely operating from the USS Harry Truman aircraft carrier. While the aircraft were flying with navigation lights and active transponders, the investigation noted that in most reported cases, crews and controllers failed to complete the required Air Traffic Incident Report Forms (ATIRF) and did not preserve cockpit voice recorder data.
Findings
- The unidentified aircraft were likely military assets operating from the USS Harry Truman.
- The incidents occurred in international waters within controlled Class A airspace.
- The presence of unidentified military traffic caused TCAS interventions and required precautionary maneuvers by civilian crews.
- While some events involved vertical separation of only 800 feet, the investigation determined there was no actual risk of collision in the analyzed cases.
- There was a lack of standardized reporting by crews and controllers regarding the specific air traffic incidents.