He had been reporting regularly to police under the terms of a provisional release from custody for theft and he did not have the right to leave the country.
Several hours earlier before he was killed, Belgacem had shot and wounded a police officer with his air pistol after a routine traffic stop north of Paris before fleeing, officials said.
Later he entered a bar in Vitry-sur-Seine on the other side of Paris and opened fire with his air gun without hitting anyone. He also stole a car before arriving at the airport.
Belgacem's father, who was initially detained by police but then released, denied his son had been involved in terrorism.
Police said they were questioning a brother and cousin of Belgacem and an autopsy on the dead man would be carried out.
Conservative Francois Fillon said that France was in a "situation of virtual civil war" and spoke out against a proposal to lift a state of emergency in place since the November 2015 attacks.
Far-right candidate Marine Le Pen, running on an anti-immigration, anti-EU ticket, said the Orly attacker could have caused a "massacre".
- Reuters, AAP