Air travellers faced delays on Thursday after flight space over Belgium was closed temporarily due to a problem with a flight data processing system at Belgium air traffic controller Belgocontrol.
Brussels Airport advised travellers to check the status of their flights after what it said was an "exceptional situation".
Two hours after Belgocontrol said it was closing air space, it tweeted: "Problem with flight plan data is resolved. Belgian sky totally open again."
This summer has already seen disruption to air travel, with carriers such as easyJet, Ryanair, IAG and Lufthansa all having said they are cancelling more flights than usual because of air traffic control strikes and staffing issues, plus severe weather.
On Wednesday, flights to and from Britain were disrupted after a Heathrow control tower was evacuated after a fire alarm and British Airways experienced problems with an IT system.
Eurocontrol had experienced a failure of its flight planning processing systems in April, which led to thousands of flight delays across Europe.
Thursday's incident is down to a Belgocontrol system, Eurocontrol said.