ATHENS/MOSCOW: Flights across Greece were grounded for several hours on Sunday after a collapse of radio frequencies crippled air traffic communication, stranding thousands of travellers and bringing airport operations to a virtual standstill.

There was little clarity on what caused the disruption, which began early Sunday and quickly escalated, affecting travel plans of thousands on the busy last weekend of the holiday period.

Some overflights across Greek and regional airspace were still being serviced, but restrictions were imposed on airport operations, Greece’s civil aviation authority said.

By Sunday afternoon, limited services were restored after pilots switched to backup frequencies to keep in touch with controllers on the ground, authorities said. Greek authorities were still unsure of the cause of the blackout, which disrupted dozens of flights.

Moscow airports shut over Ukrainian drone threat

“For some reason all frequencies were suddenly lost .. We could not communicate with aircraft in the sky,” Panagiotis Psarros, chair of the Association of Greek Air Traffic Controllers, told state broadcaster ERT.

The association later said the breakdown affected all frequencies used on the ground, and some frequencies used by Athens Approach, an air traffic control unit responsible for managing aircraft arriving in and departing from Athens’s Eleftherios Venizelos airport.

The Air Traffic Controllers Asso­ci­at­ion said controllers were using all means at their disposal to ensure the safety of flights, calling the scale of Sunday’s incident “unprecedented and unacceptable” for an air traffic control system.

Psarros said the problem seemed to be a collapse of central radio frequency systems at the Athens and Macedonia area control systems, the largest air control facility in the country. It monitors the Athens Flight Information Region, a vast expanse of airspace under the control of Greek authorities.

“We haven’t been informed about the cause of this problem… certainly the equipment we have is virtually ancient. We have raised this many times in the past,” Psarros said.

Authorities had managed to raise to 45 the number of flights leaving Greek airports every hour, by late afternoon, a Greek official said.

Meanwhile, three out of four of Moscow’s airports shut to air traffic on Sunday after Ukraine launched dozens of drones at the Russian capital, authorities said. The attacks led to multiple flight delays, including at Moscow’s second-busiest airport of Vnukovo, Russian media reported.

Ukraine, which has itself endured waves of Russian drone strikes throughout the nearly four-year war, did not immediately comment. A spokesman for Russian aviation regulator Rosaviatsia announced the closures between 1300 GMT to 1400 GMT.

“The restrictions are necessary to ensure flight safety,” Artem Korenyako said on Telegram. Each of the airports — Vnukovo, Domodedovo and Zhukovsky — partially re-opened less than an hour later, he said in later posts.

Published in Dawn, January 5th, 2026