Unions are worried about under-manning, made worse by the transfer. Charleroi airport already has too few ATCs, they say, and the cut in numbers from 18 to 16 was the last straw.

At the root of the problem lie the severe financial problems experienced by Belgocontrol, the company that runs air traffic control in Belgium. Earlier this year, a member of the Belgocontrol board warned that worn-out equipment, especially outdated radar, could be responsible for a disaster. He warned of a "Buizingen in the air," referring to the rail accident last February in which 18 people died and 171 were injured.

Federal mobility secretary Etienne Schouppe, however, brushed the warning aside. "I don't see how radar that was working perfectly today should suddenly become a danger." Belgocontrol nevertheless ordered the new radar, adding to their financial crisis.