The suspect, dubbed the 'Man in White', was spotted in CCTV images taken in Zaventem Airport moments before the first bomb exploded.
He was pictured alongside two accomplices, who died in the blast. All three were pushing trolleys laden with suitcases that are thought to have contained the explosive devices.
Fresh surveillance footage seen by the media for the first time today shows the suspect fleeing the scene shortly after a blast tore through the departures hall of the international airport.
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Belgian prosecutors said the suspect, also known as the ‘man in the hat’, had discarded the light-coloured rain mac he was wearing immediately after the bombing.
Video showed him running and walking at various different points, including past a nearby Sheraton hotel and an Avis car rental office.
He was later spotted just wearing a shirt with the sleeves rolled up.
New footage of Brussels bombing suspect
The police, heavily criticised for a string of errors in the aftermath of the attacks, are appealing to the public to help trace the man.
They hope his distinctive white rain coat, dark hat and trainers could offer clues that will lead to his arrest.
Thirty-five people were killed in the attacks - claimed by Islamic State militants - on Brussels airport and the Metro.
In the aftermath of the attacks, police carried out a number of raids across Belgium.
But investigators remain puzzled as to the whereabouts of the mystery third suspect.
Police initially wrongly named the unidentified man as Najim Laachraoui, one of the two suicide bombers who died in the airport blast.
Laachraoui died alongside Ibrahim El Bakraoui, whose brother Khalid blew himself up on the Brussels Metro on the same day.