Belgium's biggest carrier Brussels Airlines said it had cancelled all of its flights out of the Belgian capital on Wednesday due to a national strike.

(File photo: AFP)

Brussels Airlines is "eliminating its entire 222-flight schedule. The travel itineraries of more than 16,000 passengers are impacted," the Lufthansa subsidiary said in a statement on Friday.

Flights from German carrier TUI fly will also be diverted out of Belgium to airports in neighbouring France and the Netherlands, the company told the Belga news agency.

Unions warned De Morgen newspaper that all commercial flights may be forced out of Belgian airspace Wednesday if air traffic controllers joined the action.

Several Belgian unions are demanding salary hikes for all sectors of the economy, with the whole country expected to be at a standstill on Wednesday.