Greek aviation authorities are continuing to investigate the exact causes of a major disruption that occurred on Sunday, 4 January 2026, affecting air traffic control frequencies in the Athens Flight Information Region (FIR) and causing flight delays across Greece and parts of Europe.
In an official statement οn Tuesday, the Hellenic Civil Aviation Authority said the incident was caused by a failure in telecommunications infrastructure and not by a cyberattack, dispelling early concerns about a possible digital security breach.
The issue was reviewed during a meeting at the Athens and Macedonia Area Control Centers, where senior officials of the aviation authority met with a special committee appointed to investigate the disruption. According to preliminary findings, the blackout that led to hours of delays and significant operational disruption at Athens International Airport Eleftherios Venizelos was linked to technical problems rather than malicious interference.
The authority reported that the incident began at 08:59 local time, when persistent interference appeared on air traffic control frequencies. This interference affected voice communication systems, telephone networks and HELLASCOM data circuits. Although both primary and backup Voice Communication Systems and radio transmitters were available, the interference rendered the frequencies unusable.
The aviation authority activated its crisis response procedures immediately. Working in coordination with EUROCONTROL, Greek airspace was temporarily cleared to ensure safety. Operations within the Athens FIR began to recover gradually after midday, with telecommunications systems fully restored by 17:00. Normal air traffic flow resumed by 17:45.
As part of the investigation, inspections were carried out at all relay stations operated by the aviation authority, while a specialized aircraft conducted an in-flight inspection of the radio frequency spectrum to detect irregularities. The authority confirmed that no evidence of a cyberattack has emerged so far.
The Hellenic Civil Aviation Authority is continuing its close cooperation with OTE to fully determine the root causes of the incident. At the same time, it is proceeding with a broader modernization program, which includes the planned introduction of 495 new VHF VoIP radio transmitters and a new voice and radio communication system for the Athens and Macedonia control centers.
In its statement, the authority stressed that the rapid response and professionalism of air traffic controllers and technical staff ensured that flight safety was maintained throughout the disruption, despite the scale of the delays and operational challenges.
