(Adds quote of mother of survivor)
By Nelson Acosta and Sarah Marsh
HAVANA, May 19 (Reuters) - Cuban authorities said the fiery crash of an aging Boeing passenger jet on Friday shortly after takeoff from Havana had killed 110 of the 113 on board, making it the Caribbean island's deadliest air disaster in nearly 30 years.
Flags flew at half-mast in Cuba on Saturday marking the start of two days of national mourning while authorities worked to recover evidence from the site of the crash and to identify the crash victims. Fifteen have been identified so far and one black box retrieved.
Authorities told a news conference on Saturday at Havana airport that 99 of the passengers killed on the domestic flight to the eastern city of Holguin were Cuban, while three were foreign tourists - two Argentines and a Mexican. Another two were Sahrawi residents in Cuba.
The six Mexican crew members aboard the nearly 40-year-old Boeing 737, leased by Cuban flagship carrier Cubana from a small, little-known Mexican company called Damojh, were also killed.
Ten Nazarene pastoral couples returning home after a retreat were among the victims, the Cuban Nazarene Church said.
Three Cuban women survived the crash, but are still in critical condition, said the head of the hospital where they are being attended.
"My daughter is a fighter, she's strong, she'll save herself," said Amparo Font, the mother of 23-year old survivor Gretel Landrove, with a trembling voice and tears welling.
Distressed relatives cried and hugged one another outside the morgue, where they gave information on loved ones to authorities to aid in the identification process. "This is a very unexpected death, she didn't deserve it. My grandmother was a strong person," said Katherine Lucia Martinez, 18, bursting into tears and clinging to her father.
Her 60-year-old grandmother was among the dead, and she was waiting with other relatives of the deceased at a Havana hotel for an update from authorities.
President Miguel Diaz-Canel on Saturday visited the morgue, a day after reviewing the site of the crash, which is the first big test of his presidency after taking the reins from Raul Castro last month.
Some locals who saw the crash say one of the engines appeared to have caught fire before the plane hit the ground.
"The plane was on fire, it flipped and then nosedived," said farmer Marino Perez Alvaredo.
Cubana leased it less than a month ago, Transport Minister Adel Yzquierdo said on Saturday, at a time when it was struggling to meet demand for flights and was serving many domestic routes by bus instead.
Earlier this month, the company was ordered to suspend flights of its six Russian built AN-158 aircraft, of which most had reportedly already been grounded, according to state-run media.
Cuba often resorts to leasing due to the decades old U.S. trade embargo which makes it difficult to acquire planes, Yzquierdo said.
It was unclear whether Cuba had worked before with Damojh which operates just three planes, according to the Mexican government.
A pilot who used to work for Damojh was quoted on Saturday by Mexican newspaper Milenio criticizing the company for lack of adequate maintenance of planes.
"I experienced several incidents in this company, like engine failure or the electrical system went when we took off from Mexico on one occasion," Marco Aurelio Hernandez was quoted as saying. Damojh declined to comment.
Cuban investigators have so far recovered the cockpit voice recorder in "good condition," Yzquierdo said, and are still looking for the flight data recorder.
Mexico has said it will also send a team of investigators from its Directorate General of Civil Aeronautics.
The crash was the worst in Cuba since a Soviet-made Ilyushin-62M passenger plane crashed near Havana in 1989 killing all 126 people on board and another 14 on the ground.
"For the love of god, I never thought I would see this," said Caridad Miranda, 45, whose sister and niece died in the crash. "They should have checked that plane well." (Reporting by Sarah Marsh and Nelson Acosta in Havana Additional Reporting by Christina Murray and Julia Love in Mexico City Editing by G Crosse and Chris Reese)