Air traffic controllers are unhappy with savings that have been made by management at the air traffic control agency Belgocontrol.
They also want pledges on early retirement at 60. Talks between management and the unions on Wednesday afternoon failed to come up with an agreement.
It can't be ruled out that there will be more two-hour strikes over the coming days. Brussels Airport that runs the airport at Zaventem (Flemish Brabant) is advising passengers to visit its website for the latest information on delays and cancellations.