About 75 percent of flights scheduled in Europe for Wednesday are expected to take place, the European Organization for the Safety of Air Navigation, or Eurocontrol, said.

The organization said in a statement it "expects approximately 21,000 flights to take place today in European airspace. On a normal Wednesday, we would expect 28,000."

"Almost all of European airspace below 20,000 feet (6,096 meters) is available and air traffic services are being provided, although restrictions are still in force in some areas," it said.

These restrictions are expected to be gradually lifted throughout the day, it added.

The body said that by the end of Wednesday over 100,000 flights in total would have been canceled since April 15.