Skeyes, the Belgian traffic control authority, said "forced to avoid air traffic" from Tuesday 10 pm local time (4:00 ET) until Wednesday at 10 pm local time.
Dominique Dehaene, a Skeyes spokeswoman, said that no commercial aircraft flying below 8,000 meters would be allowed in the Belgian airspace. He will allow the military, humanitarian and emergency flight, he said.
The strike was called by three major unions calling for higher wages. Air Skeyes traffic managers handle more than 3,000 aircraft daily, generating more than 1 million flight movements per year.
On Tuesday, Brussels airport spokeswoman Natalie Pierard, told CNN: "Expected to leave 591
On Twitter Brussels Airport asked people not to travel to the airport.