Travellers in Europe are experiencing more flight disruption after airspace above Belgium was shut down.
Belgium's airspace was closed off for landings and departures for about two hours because of a technical glitch in the data system of the air safety control centre.
Belgocontrol spokesman Dominique Dehaene said the control centre had to execute a "clear sky" operation until the issue was fixed.
Mr Dehaene said it was "a very specific problem" that created a risk that some information on flights might not be correct. Flights resumed by 6pm.
About 15 flights were cancelled and many more delayed at Brussels international airport, which handles around 650 flights a day.
Charleroi airport handles about 140.
By comparison, Heathrow, which is Europe's busiest airport, operates 1,299 daily flights.