Iranian security officials have defused a homemade bomb on board a domestic flight headed from Ahvaz, in the west of Iran, to the capital Tehran.
The Fars news agency reports that the bomb was found 15 minutes after the plane with 131 passengers took off.
The bomb had been placed in the lavatory.
The plane landed immediately in Ahvaz airport and the bomb was defused.
The incident happened two days after a bombing of a major Shi'ite mosque in the southeastern city of Zahedan killed 25 people, two weeks before the Islamic state's presidential election.