The Islamic State group claimed responsibility for the attacks that killed 32 people and wounded more than 340 others on March 22, 2016 at Brussels airport and a city metro station.
"The start of the trial is planned for the year 2020. The start date will be communicated in the autumn via a statement," Geens said in a statement.
Investigators say the attacks were ordered by militants in war-torn Syria and organised by a French and Belgian team of jihadists that has also been linked to the Paris attacks on November 13, 2015, which killed 130 people.
In all, 12 people have been formally charged with the March 22 attacks.
Officials said the trial would be held in the former NATO military headquarters, a massive complex north of Brussels that will have room for all the lawyers, staff and hundreds of civil parties in the case.
A source close to the case said the trial could begin in the autumn of 2020 and last between six and eight months.
Among the main defendants are Mohamed Abrini and Osama Krayem, who were arrested in April 2016.
Investigators say Abrini did not set off his suitcase bomb at Zaventem airport with the other two suicide bombers and was captured days later.
Abrini was filmed at a service station en route to Paris just before the November 2015 attacks there that claimed 130 lives. Salah Abdeslam, charged over the Paris attacks, was seen with Abrini at the station.
Abrini has since been charged over the Paris massacre.
Krayem was seen next to the suicide bomber at the metro station near EU headquarters in Brussels moments before the blast.
The former NATO headquarters was abandoned by the alliance last year for a new high-tech building just across the main road.