Scores of flights in and out of Brussels' main Zaventem airport were delayed or cancelled on Monday as a result of a walkout by baggage carriers.
Airport officials said thousands of passengers were affected by the strike, which was called by Aviapartner workers to protest against harsh working conditions.
Belgian media quoted trade union officials as saying that the number of workers asked to attend each carousel shift had been reduced from five to three. Management disputed the claim, saying any reduction in personnel was caused by "unforeseen circumstances", such as flight delays.
The airport's website showed dozens of flights being either delayed or cancelled as a result of the strike. Many had to be rerouted to other airports, such as Liege's Bierset.
More than 25,000 passengers had been expected to depart from Brussels airport on Monday, with almost as many expected to arrive.