Flights were mostly suspended at Europe’s busiest airport in Istanbul and land transport largely resumed while a snowstorm forced schools to close and caused power outages in Athens on Tuesday. Heavy snowfall pummelled through both cities, paralyzing life and causing traffic chaos. The Istanbul Airport opened on Tuesday only one runway to allow flights from overseas such as the US, Canada and Mexico land, the operating firm and national carrier Turkish Airlines confirmed to dpa. Earlier on Monday, the roof of a cargo building collapsed at Istanbul airport. No casualties were reported. No plane…