"The decision to suspend our flights has been taken in order to guarantee the safety of passengers," Abdullah Al-Ajhar, assistant director-general of Saudia, said.

He added that all passengers on Monday's Kingdom-bound flight from Washington and the Jeddah-New York flight had been informed by telephone about the cancellation.

"The airline apologizes to our customers for taking the emergency measure due to a situation beyond our control. It has put all its resources to help passengers affected by the emergency measure," Al-Ajhar said. Passengers would be able to alter their bookings or change tickets.

He said that the airline did not have any idea when flights would be back to normal.

"Saudia has ordered its officials in the Kingdom and the US to offer all assistance and support to its passengers," he said.

On Saturday, a Saudia official had expressed the hope that there would be no repetition of the sky closure last month when ash from the Icelandic volcano grounded three quarters of flights over Europe and left tens of thousands of air travelers stranded. Over 2,000 passengers, mainly Umrah pilgrims, were stranded in Jeddah alone.

Meanwhile, travelers in Europe face fresh air traffic disruptions as the volcanic ash cloud started drifting back to the continent. European air traffic agency Eurocontrol said Monday areas of higher ash concentration could move from over the Atlantic Ocean back toward the Iberian Peninsula, threatening fresh airspace closures in Portugal and Spain.

Europe has been dogged for weeks by repeated shutdowns of air traffic since an erupting volcano under the Eyjafjallajokull glacier in Iceland started spewing ash in April. Hundreds of flights were cancelled over the weekend after the shifting cloud sparked fresh fears of engine-clogging ash.

Volcanic ash is abrasive and can strip off aerodynamic surfaces and paralyze aircraft engines. It can also damage aircraft electronics and windshields.

Italy and Germany reopened their airspace on Sunday, but restrictions were left in place in parts of Austria, Britain Portugal and Spain. Spanish airports operator AENA said that from 1400 GMT until at least 1800 GMT restrictions to stop planes flying between 20,000-35,000ft would reduce capacity at Madrid, Barcelona and Seville airports by 25 percent.

— With input from agencies