A widespread radio frequency outage in Greece on Sunday caused a nationwide suspension of flights, stranding thousands of travelers and halting airport operations. Air traffic controllers reported a sudden loss of communication frequencies, impacting systems at Athens and Macedonia control centers. While some overflights continued with restrictions, all arrivals and departures were grounded for several hours. Authorities are investigating the cause, with the air traffic controllers' association citing potentially obsolete equipment. Limited services began resuming by Sunday afternoon as backup frequencies were utilized.