PORT HARCOURT, Nigeria (AP) -- Grieving relatives of the 107 victims of a weekend jetliner crash struggled Monday to identify the bodies of loved ones, most of them schoolchildren, after Nigeria's second major air disaster in as many months.
President Olusegun Obasanjo sang hymns at the Ignatius Loyola Jesuit College in the capital, Abuja, where 71 of the plane's passengers were students, and ordered flags lowered to half staff, beginning three days of national mourning.
He offered his condolences to grieving families and friends, calling on all Nigerians to ''be prepared to meet our God whenever and wherever the call is made.''
Investigators examined the plane's flight-data recorders, or black boxes, as they tried to find out what caused Saturday's crash of a Sosoliso Airlines DC-9 ferrying dozens of students home for Christmas.
Flight 1145 from the capital, Abuja, was carrying 110 people when it crashed while landing in stormy weather in the southern oil city of Port Harcourt.
''We are very, very sad that this happened, especially because of the loss of the schoolchildren,'' Sosoliso's managing director, Oscar Ikwuemesi, said Monday.
The three survivors are being treated for severe burns at two hospitals, said Uriah Etawo, head of the University of Port Harcourt Teaching Hospital.
The students on the plane were between the ages of 12 and 16.
Valentina Chigbo sat Monday at the front of a mortuary after coming to identify the remains of her 16-year-old daughter, Chinenye, who was planning to take her final exams in January.
''I just feel like part of my life is gone. She was my only child, she was the center of everything in my life,'' said Chigbo, among about 50 friends and family gathered outside the Teaching Hospital's mortuary.
Chigbo identified what she believed were the remains of her daughter Saturday, but now another family has claimed the badly damaged corpse, and its identity remains in dispute.
At the morgue's rear, a car could be seen with a white-and-gold coffin inside, readying to transport a corpse for burial.
Daniel Ilabor said all three of his children -- a boy and two girls -- were killed.
''This is the saddest day of my life. Now I have nobody to call me Daddy,'' he said at his home in Port Harcourt.
It was the second major air accident in seven weeks in Africa's most-populous nation, and Obasanjo promised to overhaul Nigeria's civil-aviation structures.
''I will not jump to conclusion as to why it happened but I would want us to know why,'' he said Monday.
One survivor, a doctor named Priscillia Alaigba, lay swaddled in bandages at the Teaching Hospital's intensive care unit, with only her toes, face and neck visible. Alaigba was the most seriously injured of the three survivors, with severe burns over 60 percent of her body, Etawo said.
''She's not out of danger,'' Etawo said. ''If she survives the next two weeks I think the battle has been won.''
The other survivors have burns over as much as 40 percent of their bodies and are being treated in a clinic run by the Shell oil company. Reporters were not granted access.
More relatives gathered at another hospital in the city, where about a dozen corpses were spread on the grass outside its mortuary.
Women wailed as companions led them to identify the bodies of children and adults, which were being treated by morticians. One man was asked to identify a headless corpse.
Mourning relatives criticized airport authorities for what they say was a slow response by firefighters and poor information from aviation officials on what was being done with bodies following the crash.
Pope Benedict XVI sent his condolences Monday to the families of the victims and offered prayers for relief workers at the site of the accident.
The pontiff ''commends the dead to the eternal mercies of Almighty God and invokes the divine blessings of strength and peace upon all who mourn and upon all engaged in the work of relief,'' said the telegram sent to Port Harcourt Bishop Monsignor Alexius Obabu Makozi and released by the Vatican.
The twisted, charred wreckage lay Sunday in two principal parts several hundred yards apart, with investigators picking through the pieces searching for clues why the plane crashed.
The weather had been stormy around the airport at the time of the crash, National Civil Aviation Authority spokesman Sam Adurogboye said. Witnesses said they saw lightning as the plane approached the runway.
The Serb national airline that sold the plane to Sosoliso in 2002 said Monday the craft was built in 1973 and did not meet European standards when it was sold because its engines exceeded noise levels.
The plane still bore the Serbian registration code, YU-AJH, when it crashed, the company said.
Ikwuemesi offered assurances that his company's aircraft were safe, saying: ''We're operating to the highest standards.''
Nigerian-owned Sosoliso, established in 1994, began scheduled flights as a domestic airline in July 2000 and now flies to six Nigerian cities. The Port Harcourt crash is the first recorded by the airline. Sosoliso has not made a public statement on the crash.
Nigerian airports have come under criticism in recent months following a string of near-misses and an incident in which an Air France passenger jet crashed into a herd of cows on the runway at Port Harcourt.
International airlines briefly suspended flights at Lagos' international airport because of holes in the runway.
On Oct. 22, a Bellview Airlines Boeing 737-200 crashed after taking off from Lagos, Nigeria's biggest city, killing 117 people on board. The cause remains unclear, but U.S. investigators ruled out terrorism, a Nigerian Aviation Ministry official said last month.
After the October crash, Obasanjo ordered stricter safety and maintenance procedures for all Nigerian aircraft, directing the Aviation Ministry to ''plug loopholes'' to ensure passenger safety.
Associated Press reporters Bashir Adigun in Abuja and Onyema Godwin in Port Harcourt contributed to this report.
On the Net:
Sosoliso Airlines: http://www.sosolisoairline.com