It will take months to fully reopen Brussels airport, its CEO has warned, as staff return to the site a week after it was targeted by radical Islamist bombers.
Arnaud Feist said the building will have to be rebuilt "from the air conditioning to the check-in desks".
The airport said later it would remain closed on Wednesday, dashing hopes it would resume partial services.
32 people were killed and 96 are still in hospital after bombs targeted the airport and a metro train.
EU institutions reopened on Tuesday, amid beefed-up security measures. Increased searches on bags and vehicles are being introduced at the European Parliament while many events organised by non-EU bodies have been suspended.
Some 800 airport workers were asked to return to work on Monday to test provisional arrangements involving a temporary check-in area. Enhanced security measures are being introduced in the temporary building and further screening of baggage will take place before passengers reach the departure lounge.
The airport will only be allowed to reopen if the government gives the green light, with an initial target of 800 to 1000 passengers per hour as opposed to the airport's average of 5000.
"The provisional structure will not be able to absorb the usual number we had before the attacks," Mr Feist told Belgian media.
"Although the structure of the building is intact, it will all have to be rebuilt, from the air conditioning to the check-in desks. And that will take months," he predicted.
He said he hoped that the airport would open at 20 percent capacity on Wednesday, but a later tweet from airport authorities said it would remain closed.
Police resumed their hunt for one of the three men who blew up the airport on Sunday, after they released a man named by Belgian media as Faycal Cheffou for lack of evidence.
He had wrongly been suspected of being the man pictured by CCTV, wearing a hat and a light jacket. However he still faces allegations of "terrorist assassination".
The federal prosecutor said "clues that led to his arrest were not substantiated by the ongoing inquiry".
Several suspects have been arrested in Belgium and other countries in recent days
- An Algerian named as Djamal Eddine Ouali was being questioned in Italy on suspicion of forging identity documents used by Paris attackers, including detained Belgian suspect Salah Abdeslam
- Yassine A, Mohamed B and Aboubaker O were held after raids on Saturday in Belgium and accused of belonging to a terrorist group
- Reda Kriket, 34, was arrested in Rotterdam on suspicion of planning another attack in France
- Abderamane A was arrested in Brussels when he was shot in the leg at a tram stop last Thursday