The word “chaos” comes from the Greek language, and proved an apt description on Sunday, when a major air traffic communications failure grounded hundreds of flights and triggered disruption across Europe, before services were gradually restored later in the day.
The incident occurred when the radio frequency system used to coordinate flights in the Athens and Macedonia Area Control Centres suddenly collapsed. These centres oversee the country’s Flight Information Region (FIR), which means that all departures and landings across Greece were suspended and the national airspace shut down.
🇬🇷 Thousands of people were stranded at airports across Europe after a disruption led to the closure of Greek airspace.
— Visegrád 24 (@visegrad24) January 5, 2026
The aviation outage hit during the peak holiday travel period, as thousands of passengers were returning home from New Year vacations via Greece.
The day… pic.twitter.com/wf0X3fKXjd
The failure occurred in the early hours of 4 January when multiple radio frequencies went offline. These frequencies are essential for communication between pilots and air traffic controllers, ensuring flight safety. After this happened, the Greek aviation authorities issued a NOTAM (Notice to Airmen) and suspended all activity at airports nationwide to prevent accidents.
In a statement, they explained that an unknown “noise” observed in the frequencies was impacting radio channels in the form of “continuous, involuntary emission,” the cause of which was not clear.
Aircraft already in the air were handled manually, while others were rerouted or diverted to neighbouring countries, including Italy, Turkey, and Cyprus.
As a result, Aegean Airlines cancelled dozens of flights, mainly to and from Athens, and informed its passengers that this was due to “a technical issue affecting the radio frequency systems of the Hellenic Aviation Service Provider, ongoing since the early morning and causing a significant reduction in capacity within Greek airspace.”
Announcement: We would like to inform our passengers that the technical issue affecting the radio frequency systems of the Hellenic Aviation Service Provider, which has been ongoing since the early morning hours continues to cause a significant reduction in capacity within Greek…
— Aegean Airlines (@aegeanairlines) January 4, 2026
EasyJet told its passengers the cancellations “outside of the company’s control” were due to an airspace closure at Athens airport and “considered an extraordinary circumstance.”
BA’s flight to Athens was either cancelled or grounded in the country.
As a result, thousands of passengers were left stranded at major hubs such as Athens International Airport, Eleftherios Venizelos, as well as regional airports in Thessaloniki and Heraklion. The disruption occurred during one of the busiest travel weekends of the year, when passengers were returning to work and school after the Christmas and New Year holidays. Athens alone typically handles more than 600 scheduled flights per day.
Passengers complained of a lack of information throughout the incident.
🚨 #BREAKING Severe air traffic disruptions due to a communications failure in #Greek #ATC, #Athens & #Makedonia #FIR, causing major delays. #Greece has declared Zero Rate airspace until 14:00utc#Aviation #Greece #AirTraffic #Flights@fl360aero @OnDisasters @flightradar24 pic.twitter.com/1yRxUNWarw
— Aviation News Israel (@AviationNewsIL) January 4, 2026
“We have no updates,” said one passenger, while another, who had been on a flight to Rhodes before it was forced to turn back to Athens, told Reuters, “From that moment until now, we have had no information whatsoever.”
The impact was not confined to Greece. The shutdown forced reroutes and cancellations on international services, as Greece is a busy hub for flights between Europe, the Middle East, and Asia.
The cause of the problem is still under investigation. Some suspect that outdated equipment caused the error.
Panagiotis Psarros, chair of the Greek Air Traffic Controllers’ Association, told Reuters that controllers had not been informed of the cause. He added: “Certainly, the equipment we have is virtually ancient.”
Due to a technical problem causing communication frequencies failure, a zero rate is in effect for all flights within Athinai FIR/UIR until further notice. pic.twitter.com/JPUe3Mm9bC
— Flightradar24 (@flightradar24) January 4, 2026
By the afternoon, backup frequencies and alternative communication channels had been re-established, enabling limited operations to resume, albeit with reduced capacity. Full communications were restored by the end of the day, and flights resumed as normal.
Aviation unions and industry observers had previously warned that Greece’s radar and communications systems required urgent upgrades and were already struggling to cope with rising traffic.
Under EU air passenger rights rules, travellers whose flights are cancelled are entitled to be rebooked on the next available service, including with other airlines if necessary. They must also be provided with meals, accommodation, and assistance until they reach their destination.
