Air traffic control agency Eurocontrol has warned airlines to exercise caution in the eastern Mediterranean due to the possible launch of air strikes into Syria in next 72 hours.
Eurocontrol said that air-to-ground and/or cruise missiles could be used within that period and there was a possibility of intermittent disruption of radio navigation equipment.
Russia and the United States tangled on Tuesday at the United Nations over the alleged use of chemical weapons in Syria as Washington and its allies considered whether to strike at President Bashar al-Assad's forces over a suspected poison gas attack last weekend.
"Due consideration needs to be taken when planning flight operations in the Eastern Mediterranean/Nicosia FIR area," the agency said on its website in reference to designated areas of airspace, without specifying the origin of any potential threat.
Eurocontrol's warning cited a document from the European Aviation Safety Agency, Europe's safety regulator, a copy of which was not immediately available.
Aviation regulators in countries including the US, UK, France and Germany have previously issued warnings against airlines entering Syrian airspace, but the Eurocontrol statement included a broader area outside the airspace controlled by Damascus.
Reports on Tuesday said the Syrian army had put all military positions on alert, including airports and all bases, for 72 hours.
US President Donald Trump cancelled a planned trip to Latin America later this week to focus instead on responding to the Syria incident, the White House said.
Mr Trump had on Monday warned of a quick, forceful response once responsibility for the Syria attack was established.