TEHRAN A Russian research institute is to announce the main cause of the Yak-40 plane crash which killed 30 on board, including Iran's transport minister and seven MPs, head of the Civil Aviation Organization of Iran Behzad Mazaheri said Wednesday.

He said based on the investigation carried out so far the human error seems to be the main cause of the crash.

The official called on the Majlis and the government to help solve the problems facing the Civil Aviation Organization (CAO) and to renovate Iran's aging aviation fleet.

The Russian-built Yakovlev plane (Yak-40), on lease from Armenia, crashed in northern Iran on May 17.

The two black boxes of the crashed plane along with a number of Iranian aviation experts were dispatched to Moscow to help find out the cause of the tragic air crash.