One person, accused of masterminding the raid, will hear his case in court later.
In February 2013, eight men made a hole in a security fence at Brussels’ international airport, drove onto the tarmac and stole £31m ($50m) worth of diamonds from the cargo hold of a Swiss-bound plane.
A subsequent investigation led to the arrest of more than 30 people, and 19 of them faced court in Brussels in March 2018.
Although the main suspects faced up to eight years in prison, they have all been acquitted and walked free.
The raid has been compared to the plot of the Hollywood movie Ocean’s Eleven, starring George Clooney, Brad Pitt and Matt Damon, for its clinically clean execution.
Sven Mary, a lawyer for one of the women acquitted, said the tribunal in Brussels thought the evidence presented by the prosecution was not sufficient to convict.
He said: “I believe that the tribunal thought that the evidence presented by the prosecution was not enough, and it was not enough for all (all the accused).
“Now the prosecution side may need to do a little bit of reflection, and to see if the elements they have for this case would be sufficient should they decide to appeal (the decision), and I fear that a bit.”
A fellow lawyer for an acquitted suspect, Nathalie Gallant, said: “This acquittal is the proof that prosecution failed to bring evidence on the involvement of each of the accused, and there were a lot of them.
“They made a very wide sweep, they focused on some famous names, and we reproached the investigators to have worked with blinkers and to focus on specific people rather than investigate other leads.
“So the tribunal is indirectly saying that we were right and that the case is not sufficient to condemn anyone. So it is a great result.”
The heist is one of the biggest of recent times. The robbers dressed in police uniforms, and stayed in a construction site outside the airport before the heist.
They waved Kalashnikov-style weapons, but carried out the crime in 20 minutes without firing a shot.
Passengers on the plane did not seem to know about the heist until they were told to get off as the flight had been cancelled.