President Charles Taylor issued a warning about the future of democracy in Liberia as he stepped down after six tumultuous years in charge and left the country.
Blah has been described as a Taylor-made successor
As part of moves to end more than a decade of civil war and regional instability, Mr Taylor handed over power to his vice president, Moses Blah, who takes temporary charge until October.
It was the first peaceful transition from one Liberian leader to another in 30 years.
And then at about 1700 GMT Mr Taylor boarded the plane, accompanied by Nigerian officials, which is expected to take him into exile in Nigeria.
A few hours earlier, amid tight security, Mr Taylor had told visiting regional leaders and prominent Liberians at the resignation ceremony in the capital, Monrovia, that it was crucial his departure did not lead to a new war.
Adopting a sombre and defiant tone, Mr Taylor warned that any future government should be decided by the Liberian people.
In a speech replete with religious and African imagery, he described himself as a sacrificial lamb and implied he was a victim of United States interests.
"History will be kind to me. I know I have fulfilled my duties," he said, as many of his supporters wept.
"God willing, I will be back," he concluded before handing the green sash of office to Mr Blah.
Addressing the ceremony, Mr Blah made an impassioned call for peace, urging the rebels to co-operate with the government.
Mr Taylor's resignation has been one of the main demands of rebel forces who have been advancing on the capital for the past six weeks.
The rebels also insisted that he go into exile.
"For us in Lurd, the war is over," said Sekou Fofana, a senior official in
Liberians United for Reconciliation and Democracy (Lurd).
"Once he leaves Liberia today we are not going to fight. The suffering
of Liberians is over."
Members of Mr Taylor's staff and his possessions have already arrived in the south-eastern Nigerian city of Calabar, where a hilltop mansion is being made ready for him.
The handover ceremony was attended by South African President Thabo Mbeki, Mozambique President Joaquim Chissano, representing the African Union, and President John Kufuor of Ghana, representing West Africa's regional bloc.
Mr Mbeki promised that South Africa would provide troops for the intervention force.
Mr Chissano said Mr Taylor's decision to step down gave rise to the hope that Africa and the rest of the world would turn to help Liberia achieve an irreversible peace.
Mr Taylor has in the past objected to going abroad because he is wanted by the special war crimes tribunal in Sierra Leone.
The main Liberian rebel leader, Sekou Damate Conneh of Lurd, has pledged to give international aid agencies immediate access to port facilities as soon as Charles Taylor leaves Liberia.
Mr Conneh's forces control much of the country, including the port area of Monrovia.
The BBC's Barnaby Phillips in Monrovia says the port area is Lurd's prize possession and it is hard to see them pulling out until Mr Taylor leaves the country.
Following Mr Taylor's resignation, the UN has said it will be returning to Liberia on Tuesday to resume humanitarian operations.
Aid workers have been anxious to resume supplies of food and medical aid to tens of thousands of people who have been isolated by weeks of fighting.
They say the situation is critical with warehouses looted and fighting blocking the delivery of fresh food and medical aid.
A humanitarian crisis has also been reported by the International Red Cross in the port city of Buchanan, to the east.
The city is being held by another rebel group, the Movement for Democracy in Liberia (Model).
More than 8,000 people have taken refuge in the Catholic Mission compound there, which is said to have run out of food and water.