Air Traffic Controllers' Strike Paralyzes Brussels Airport
Air Traffic Controllers working at the Brussels airport decided to hold a wildcat strike, which caused all inbound and outbound flights on Tuesday evening to be put on hold. The workers decided to hold a strike over disputes regarding pension reform. Traffic at this airport has already been reduced following the attack that happened on the airport on March 22nd. Workers who participated in the strike reported to their superiors that they were either sick or "unfit to work".
See "Air Traffic Controllers' Strike Paralyzes Brussels Airport", ABC News, April 12, 2016