chaos at Greece airports as passengers stranded after flights were grounded (AP photo)

Thousands of travelers in Greece were stranded after flights across the country had to be grounded due to sudden, unexplained loss of radio frequency reported around 0700 GMT.“No plane landed or took off for at least two hours,” said the press office at Athens airport, ” said the press office at Athens airport, as quoted by AFP. There was no immediate clarity on what caused the disruption, which began early Sunday and escalated rapidly. Greece’s civil aviation authority said that while some overflights across Greek and regional airspace were still being handled, airport operations faced restrictions for safety reasons.Dozens of flights were disrupted. “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.He called the incident “very serious” and claimed “obsolete” airport equipment was responsible for the chaos.Psarros said the issue appeared to stem from a collapse of central radio frequency systems at the Athens and Macedonia area control centres. The Athens centre, the country’s largest air traffic control facility, oversees the Athens Flight Information Region, a vast stretch of airspace under Greek control.“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.A Transport Ministry official told Reuters that some aircraft heading north and east were allowed to depart, but more than 75 flights were delayed.In Israel, an Airports Authority spokesperson said Greek airspace had been closed until 4 p.m. local time (1400 GMT), warning travellers to expect delays to arrivals and departures.