A huge manhunt netted the suspect officially identified as Faycal C -- and identified by local media as Faycal Cheffou -- and investigators are now working on the theory that he could be the man in a hat and white jacket pictured with two other airport bombers, but whose device failed to go off.
Brussels airport said it will not reopen before Tuesday at the earliest as it implements new security measures and repairs the departure hall wrecked by the bombers, believed to be from the Islamic State group.
Prosecutors meanwhile also charged a man arrested in Belgium over a new plot to hit Paris, deepening the connections in what French President Francois Hollande has described as a single terror cell straddling both France and Belgium.
The Belgian government faces a torrent of criticism at home and abroad, with key ministers on the back foot saying they had done everything possible to prevent Tuesday's attacks and track a network also linked to November's Paris attacks.
"It is an endless nightmare for a country turned upside down," said Le Soir daily in a front-page editorial.
Heavily armed soldiers and police remained on patrol in the capital and Zaventem airport.
In an indication the city is still on edge, a bomb disposal squad carried out a controlled detonation on a southern Brussels street to destroy a suspect backpack.
Pop diva Mariah Carey yesterday cancelled a show in Brussels, saying she was advised to do so "for the safety of my fans, my band, crew and everyone involved with the tour."
Prosecutors said Faycal C was one of three people arrested outside the Belgian federal prosecutor's office in Brussels on Thursday night as part of a huge sweep of detentions across Belgium and Europe.
"He has been charged with taking part in a terrorist group, terrorist murder and attempted terrorist murder," the prosecutor said.
Asked by AFP if Faycal C was the suspected third bomber dubbed the "man in the hat", a source close to the inquiry told AFP: "That is a hypothesis the investigators are working on.