The airspace over Greece suddenly emptied as flights were suspended nationwide.

Authorities said the cause of the disruption was under investigation. Greece’s civil aviation authority said some overflights through the Athens Flight Information Region (FIR) were continuing, but restrictions had been imposed on airport operations as a safety measure, according to a Reuters report.

Flight-tracking data showed Greek airspace was largely empty. State broadcaster ERT reported that arrivals and departures at airports across Greece were suspended from 9:00 a.m. local time (0700 GMT), airing visuals from the departure terminal of Eleftherios Venizelos International Airport packed with stranded travellers.

ERT said several flights were being diverted to neighbouring countries. In Israel, an Airports Authority spokesperson said Greek airspace would remain closed until 4:00 p.m. local time, warning passengers to expect delays to both arrivals and departures.

“Security Check-In Closed Since 9 AM! Due to the ongoing radio frequency failure in Greek airspace (started early January 4, 2026), NO takeoffs possible nationwide. Security check-in & departures halted at Athens International since ~9 AM,” Greek City Times posted on X.

“Massive queues building up, passengers stranded. Arrivals landing manually where possible, but many diversions/delays All Greek airports affected – FIR Athens effectively closed. Civil Aviation Authority rushing fixes, but no ETA yet. Airlines issuing alerts – expect huge delays/cancellations today,” it added.

A Transport Ministry official told Reuters that some aircraft heading north and east were permitted to depart, though more than 75 flights were delayed.

Meanwhile, an Airports Authority spokesperson in Israel said Greek airspace would remain closed until 4 p.m. local time (1400 GMT), warning travellers to expect delays to both arrivals and departures.