The airline's chief executive says there was confusion from the control tower, but the airport manager has not confirmed the claims. Witnesses say the plane abruptly changed its direction while survivors say they were not warned
Recordings show apparent confusion between the pilot and air traffic control over the runway approach moments before a plane crash-landed at Kathmandu airport, experts said on Tuesday as Nepal began investigating its deadliest aviation accident in decades.
Aviation authorities said they had recovered the flight data recorder from the charred wreckage of the plane, which burst into flames after ploughing into a football field near Kathmandu airport on Monday, killing 49 people.
Witnesses have described how the US-Bangla Airways plane carrying 71 people abruptly changed direction moments before it crashed.
TRT World's Mhairi Beveridge explains.
On Monday the airline's chief executive Imran Asif said there had been a "fumble from the control tower" as the plane approached the airport's single runway.
But airport manager Raj Kumar Chhetri said it was too early to say what had caused the mountainous country's deadliest crash since 1992.
"It is yet to be identified whether the pilot or air traffic control was wrong," he said, adding the investigation would be carried out with Bangladesh.
Recordings of the conversation between air traffic control and the pilot appear to indicate confusion over which end of Kathmandu airport's runway the plane was to approach.
Air traffic control can initially be heard clearing the plane to land from the southern approach.
"You are going towards runway 20," the controller is heard saying seconds later, referring to the northern end of the tarmac.
A series of confused messages follow just before the crash in which the pilot says they will land at "runway 20" and then "runway 02" – the southern end.
"There is certainly considerable confusion from air traffic as to which runway the aircraft actually wants to land on," said Britain-based aviation expert Andrew Blackie, who has reviewed the recordings.
Survivors said the pilot gave no warning to passengers as the plane abruptly changed direction just before the crash.
"I had asked the air hostess, what is happening, is everything fine? She gave a thumbs up, but I could see she was panicking," said Ashish Ranjit, 35, who escaped through a window on the plane's right.
"It was so low, and it took such sharp turns."
The plane hit the runway and skidded through an airport fence, leaving a trail of fuel and coming to a stop in a field where it burst into flames.
Twenty-two passengers – mostly sitting on the plane's right side – managed to free themselves from burning wreckage by climbing through the plane's windows or were pulled from the fuselage by passengers and rescuers.
Kathmandu airport lies in a narrow bowl-shaped valley with the Himalayas to the north, making it a notoriously challenging place to land.
Kathmandu's skies have also become increasingly crowded in recent years as air travel has boomed, but investment in critical infrastructure has lagged.
The head of Nepal's civil aviation authority rejected suggestions that the airport's creaking facilities played a role in the crash.
"The accident has not occurred because of the airport's infrastructure ... Indeed it is operating in a situation of congestion, but we have procedures to safely land flights despite traffic," Sanjiv Gautam told reporters.
Nepal has a poor road network, and internal flights are key to accessing its remote regions.
The country has suffered more than 20 aviation accidents in the last decade, mostly involving small planes on domestic routes.
"There are reasons why Nepal has such a relatively high accident rate, many of those are because of the challenges of operating in mountain airfields that surround Nepal," said Blackie, who was part of a team that probed a 2016 crash of a small turboprop plane in Nepal.
But experts say the Canadian-made Bombardier Dash 8 Q400 is a manoeuvrable plane that was developed to fly in Canada's harsh arctic north and should be at home in Nepal's mountainous terrain.
Bombardier is sending two members of its air safety team to support the air crash investigation. The pair left Canada on Tuesday morning, the company said.
Relatives of the Bangladeshi crash victims arrived in Kathmandu on a special charter flight on Tuesday. There were tearful scenes outside the morgue where most of the dead have been taken.