A CCTV picture of the suspect shows a bespectacled man with a goatee beard, wearing a white jacket and black hat, and pushing a trolley with a large black bag.
Authorities earlier released a grainy picture of the same man alongside two men with dark hair who were also pushing trollies with similar bags.
Both of those men wore black gloves on their left hands.
Belgian officials said there were two bomb blasts in the main airport hall this morning, at least one of which was a suicide bombing.
"Three bombs were brought into the building, of which one failed to explode," Lodewijk De Witte, the governor of Flemish Brabant province, told a press conference at the airport.
He said it was later destroyed in a controlled explosion.