A Bangladeshi airliner was misaligned with the runway and its pilot was disoriented and tried to land in 'sheer desperation' when the plane crashed last year in Nepal, an investigation report said.

US-Bangla Airlines Flight BS211 from Dhaka crashed on its second landing attempt at Kathmandu's Tribhuvan International Airport on March 12, 2018. The 51 people killed were 28 Bangladeshi, 22 Nepalese and one Chinese national, and 20 others were injured. The pilot and co-pilot were among the dead.

The investigation report compiled by Nepalese officials and made available Monday said the probable cause of the crash was the pilot's disorientation and loss of situation awareness.

'Contributing to this, the aircraft was offset to the proper approach path that led to maneuvers in a very dangerous and unsafe altitude to alight with the runway. Landing was completed in a sheer desperation after sighting the runway, at very close proximity and very low altitude,' it said.

The report also said the pilot had been released from the Bangladesh Air Force in 1993 due to depression and was only allowed to fly civilian planes from 2002 after a detailed medical evaluation.

Also, the pilot was under stress and emotionally disturbed and had lack of sleep in the preceding night.

The report also cited a lack of assertiveness from controllers at Kathmandu airport in monitoring the flight path and failing to issue clear instructions to carry out a standard missed-approach procedure.

The flight crew and the controllers also lacked a clear understanding of each other when they communicated about the landing runway, the report said.

The report recommended that assertiveness in such situations become part of the training for air traffic controllers.

It also asked the Bangladesh civil aviation authority to reassess the physical and psychological status of grounded pilots before their licenses are renewed and that all airline pilots undergo psychological evaluation during training.