A massive failure of air traffic control radio frequencies grounded flights across Greece for two hours Sunday, stranding thousands of passengers during the peak holiday return rush.
Officials halted departures and severely restricted landings after controllers lost the ability to communicate with aircraft throughout the Greek Flight Information Region (FIR).
Operations began to gradually resume by late morning, though authorities warned of cascading delays throughout the day.
Olga Toki, vice president of the Greek Air Traffic Controllers Association, described the outage as a critical safety hazard.
“We cannot communicate with flight crews. We cannot issue instructions, and they cannot receive them,” Mrs. Toki told local media.
“That means flight safety cannot be guaranteed.”
Mrs. Toki noted the breakdown began around 9 a.m., effectively emptying Greek airspace. While Athens approach control retained limited functionality—allowing some aircraft already on final descent to land—flights attempting to enter from the northern and western borders were blocked.
“Aircraft coming from the northern borders could not transit Greek airspace to reach Athens because there was no communication at all,” Mrs. Toki explained.
She dismissed speculation of a cyberattack, attributing the collapse to a large-scale technical malfunction of the frequency network.
Civil aviation authorities have launched an immediate investigation into the cause of the failure. Airlines are urging all passengers to check flight statuses before heading to airports as schedules slowly normalize.