Iran's President Hassan Rouhani has demanded an apology from the US government for downing an Iranian passenger flight in 1988 after more than three decades.On July 3, 1988, a surface-to-air missile fired from a US warship stationed in the Gulf hit the Iran Air Flight 655, an Airbus A300, killing all 290 occupants on board, reports Xinhua news agency.Addressing a meeting on Saturday, Rouhani said: "The US government has to know that it committed a very big crime in the Gulf in 1988."US apologies, compensation, and an explanation about the reason why awards were given to "the killers and perpetrators of this great crime" are still expected, Rouhani noted.Following the downing of the flight from Tehran to Dubai, Washington had claimed that its forces were acting in self-defense after having mistaken the airliner for a F-14 Tomcat jet fighter.The crew of the US ship received awards at the end of their mission.As part of the settlement, even though the US government did not admit legal liability or formally apologise to Iran, it agreed to pay $61.8 million on an ex-gratia basis in compensation to the families of the Iranian victims.It was considered was the deadliest aviation disaster involving an Airbus A300.