A convoy of more than 100 cars and bikes marked the 46th anniversary of the Birmingham pub bombings.
Friends and family of the 21 people killed in the 1974 attack lined the streets before ending at West Midlands Police's headquarters.
Campaigners and community leaders are calling for a public inquiry to establish "justice and accountability".
A 65-year-old man was arrested over the bombings on Wednesday in Belfast and was released on Friday after questioning.
An inquest last year ruled the victims were unlawfully killed, but failed to establish who was responsible.
The hearings followed years of campaigning by the affected families calling for a full account into the events that happened that night.
Home Secretary, Priti Patel, last month said she would be considering a public inquiry into the bombings.
Six men - Hugh Callaghan, Paddy Hill, Gerard Hunter, Richard McIlkenny, William Power and John Walker - were wrongly jailed for life in 1975 for the bombings.
The so-called 'Birmingham SIx' had their convictions quashed in the appeal court and were released in 1991.