Flights have been suspended across Greece after unspecified issues affecting radio frequencies.
Airports halted arrivals and departures for safety reasons from 9am local time (7am in the UK).
Flight trackers show Greek airspace largely empty.
Athens’s Eleftherios Venizelos airport has become crowded with travellers unable to board.
Flights have been diverted to neighbouring countries, according to state broadcaster ERT.
Authorities said they were investigating the cause of the issue.
This is a breaking news story and will be updated.
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