Brussels and Brussels South Charleroi Airports could be severely impacted with up to 70,000 travellers affected.
The strike is set for October 14 with ground staff and airport security expected to join the industrial action.
Brussels South Charleroi Airport could see all flights cancelled while Brussels Airport is expected to ground all departing flights.
A key northern European hub, Brussels handles about 200 departures a day.
It is served by flights from London Heathrow, Birmingham, Manchester and Edinburgh.
It is still unclear how extensive the strike action will be.
“Due to the national trade union action on Tuesday October 14, in which the staff of the security service provider are participating, we unfortunately expect a major impact on our airport operations,” the airport said.
“In order to guarantee the safety of our passengers and staff, we have decided, in consultation with the airlines, not to allow any departing passenger flights.”
Brussels Charleroi Airport also released a statement “Due to the national day of action and the lack of staff present to ensure safe operations, all flights scheduled to and from Charleroi Airport will be cancelled.”
The union movement is opposing government proposals to raise the retirement age, and revise pensions.
There was a previous strike at Brussels Airport in February over the same issues.