Industrial action by French air traffic controllers led to flight cancellations at Belgian airports on Wednesday, local media are reporting.
The strike has affected flights with intended destinations in France, as well as flights using French airspace to destinations such as Spain and Portugal.
Four out of ten flights travelling to and from France are being affected by the dispute.
The main Belgian carrier, SN Brussels, has been forced to cancel flights between Brussels and Nice.
However, flights to Paris, Marseille, Montpellier, Strasbourg and Toulouse have not been disrupted.
SN Brussels spokesperson, Geert Sciot, has not ruled out the possibility of delays on these services. "Most of our flights are operational and we will make sure to offer alternatives to accommodate passengers," he said, quoted by Le Soir.
The company said it will reroute passengers to places close to their intended destinations, if possible.
In addition, the low-cost airline Ryanair announced the cancellation of 250 European flights on Wednesday, including from Brussels and Charleroi airports in Belgium to Barcelona, Lisbon, Malaga, Nimes, Palma de Mallorca, Porto and Santander.
French air traffic controllers are on strike on Wednesday and Thursday over a pay dispute. The French civil aviation authority, DGAC, asked airlines to cut flights to and from France by 40 percent on Wednesday. Short-haul flights are set to be the worst affected.
Further action is scheduled to take place on 16-18 April and again on 29 April to 2 May.