Italian police said the hijackers had given themselves up after a short period of negotiations.
Turkish television initially quoted police sources as saying the plane had been hijacked in protest at a planned visit to Turkey next month by the Pope, who offended many Muslims with a speech last month linking the spread of the Islamic faith to violence.
But Turkish television later reported one of the hijackers had converted to Christianity and was a conscientious objector.
It said he had sent a letter to the Pope in late August, asking for his help to avoid compulsory military service in Turkey. It quoted the letter as reading: “I am a Christian and I do not want to serve in a Muslim army.”