* Investigators retrieve flight data recorder
* Pilot landed more than 100 times at Kathmandu - airline
* Death toll 49, including four crew - officials
* Transcript suggests confusion over runway (Adds airline's defence of pilots)
By Gopal Sharma and Ruma Paul
KATHMANDU/DHAKA, March 13 (Reuters) - A Bangladeshi airline said on Tuesday its two pilots aboard the plane that crashed in Nepal killing 49 people had both received special training to land at Kathmandu airport and had successfully handled previous flights.
The airline and airport authorities in Kathmandu have blamed each other in the aftermath of Monday's disaster, the Himalayan nation's worst since the 1992 crash of a Pakistan International Airlines aircraft killed 167 people.
Flight operator US-Bangla Airlines said it was too early to blame anyone, after a transcript of the pilots' radio conversation with ground control in Kathmandu revealed confusion over the designated runway.
Captain Abid Sultan and co-pilot Prithula Rashid died when their plane crashed short of the runway, broke into pieces and caught fire, officials said.
"Sultan was experienced, quite familiar with the airfield and the aircraft," US-Bangla spokesman Kamrul Islam said. "Rashid was also specially trained to make landings at the airport. This is mandatory for any pilot to fly over there. She also made landings at the airport before."
Investigators have retrieved the flight data recorder from the wreckage, said Raj Kumar Chettri, the airport's general manager, and an investigation had begun into the cause of the crash.
The Bombardier Q400 series aircraft was carrying 71 people from the Bangladeshi capital Dhaka when it tried to land in visibility that weather officials said exceeded 6 km (4 miles), with cloud at one end of the runway and a light tailwind of six to seven knots.
A Nepali army official said one of the 22 survivors being treated in Kathmandu hospitals was to be discharged on Tuesday. Families of some of the victims mourned outside the hospitals.
There were 33 Nepali passengers, 32 from Bangladesh, one from China and one from the Maldives.
US-Bangla said Sultan, a former Bangladesh Air Force pilot, had landed more than 100 times at Kathmandu, where wind shear and bird hits are frequent hazards in the mountainous region.
Sultan had more than 5,000 hours flying experience and was specially trained to land at the airport, Islam said.
The airline also denied a media report that the aircraft had skidded off the runway during a domestic flight in 2015, saying it "never, ever encountered any accident. It had no technical glitches."
Defending the pilots, airline chief executive Imran Asif cited the transcript of their radio conversation with ground control in Kathmandu issued by a German air safety website, JACDEC.
The Civil Aviation Authority of Nepal did not directly confirm the authenticity of the transcript, saying publication of such exchanges went against the law.
"We suspect wrong signals from Kathmandu air traffic control room might have led to the crash," Asif told reporters on Monday. "A three-minute conversation between the pilot and the air traffic control before the landing indicated that they sent a wrong signal to the pilot."
Transmissions by the Kathmandu tower controller show that, despite being cleared to land on runway 02, the flight began deviating from its course.
The captain and the tower controller discussed which runway the aircraft was aiming for, the website said. At one point, the controller told the co-pilot she was heading toward runway 20, although the aircraft had been cleared for runway 02.
Later, the captain took over the conversation and confirmed the plan to land at runway 02. At one stage, ground control said runway 20 had also been cleared for landing, however.
The plane made an attempt to land on the runway it was originally meant to use.
Chettri said most international flights are directed to runway 02 but depending on wind conditions, flights are also requested to use 20.
He said police would investigate how the conversation between the pilots and control room was leaked.
On Tuesday, airport operations returned to normal. The aircraft wreckage lay on ground near the runway, guarded by security personnel.
"Regardless of what contributed to this tragic accident, we are sorry," Asif, the airline's chief executive, wrote on networking website LinkedIn. "And we stand by the bereaved families of those who lost their loved ones."
On Monday, Kathmandu airport officials said they had asked the pilots if they faced a problem after the aircraft changed course in the final descent, but the pilots said they did not.
The plane was then seen circling twice in a northeast direction, Chettri said. Traffic controllers again asked the pilot if things were OK, and he replied, "Yes".
The tower then told the pilot his alignment was not correct, but received no reply, Chettri said.
Canadian plane maker Bombardier said it was sending an air safety investigator and a field service representative to the site.
Reporting by Gopal Sharma in Kathmandu and Ruma Paul in Dhaka; Additional reporting by Allison Lampert in Montreal; Writing by Krishna N. Das; Editing by Sanjeev Miglani, Clarence Fernandez and Janet Lawrence