Greece’s Civil Aviation Authority (HCAA) described a large-scale disruption of the Athens Flight Information Region (FIR) as an unprecedented operational shock, underscoring structural fragilities in aviation communications infrastructure. 

The incident, which unfolded on Jan. 4, 2026, combined widespread radio-frequency interference with simultaneous failures in critical communication lines, forcing authorities to restrict traffic flows for safety reasons rather than technical convenience.

According to the authority’s statement, the disruption began at 08:59 local time and involved “mass interference in almost all frequencies serving the Athens F.I.R.” 

The scale was compounded by a concurrent outage of HELLAS COM lines and operational telephone communications, sharply constraining coordination capacity.

The authority characterized the event as a “πρωτοφανές περιστατικό,” describing it as unprecedented “in terms of its scale, geographical extent, and temporal persistence.”

Technical assessments indicated that the interference manifested as persistent background noise rather than intermittent spikes. 

The authority said the noise took the form of a “continuous, unintentional emission,” complicating isolation and mitigation efforts.

Engineers from the aviation authority worked alongside technicians from OTE, Greece’s main telecommunications provider, to identify and restore affected systems.

In parallel, the authority activated its Crisis Management Team early Sunday morning under its administrator, convening senior aeronautical and technical leadership at the Athens Area Control Center.

The team remained in continuous coordination with external bodies, including EUROCONTROL, to manage airspace safely while systems were under stress.

With communications degraded, the Athens Area Control Center reduced throughput as a precautionary measure.

Aircraft handled within the Athens FIR were cut to 35 aircraft per hour, a significant restriction in one of southeastern Europe’s busiest airspace regions. 

After partial stabilization, capacity was raised to 45 aircraft per hour after 16:00 local time, though disruptions had already caused delays and cancellations across Greek airports.

To accelerate diagnosis, the authority ordered the emergency deployment of a specially equipped HCAA aircraft, carrying agency electronics specialists and a technical expert from the Hellenic Telecommunications and Post Commission (EETT). 

The aircraft conducted targeted airborne monitoring to trace the source and characteristics of the interference.

Ground inspections were conducted simultaneously at transmission and reception sites across multiple regions, including Mount Hymettus, Pelion, Thasos, the Acarnanian Mountains, Monastiri, and the Gerania range. The breadth of these checks reflected concerns that the disruption was neither localized nor short-lived.

The authority emphasized that all measures were taken with flight safety as the overriding criterion.