The flight's captain, aged 52, was released in 1993 from the Bangladeshi Air Force because he suffered from depression but was later declared fit to fly civilian aircraft, the report said, with recent medical reports mentioning no symptoms.
Citing the voice recorder and the eyewitness accounts of passengers, the report said the captain was smoking in the cockpit during the flight and "engaged in unnecessary, unprofessional and lengthy conversation even in the critical phase," violating the norm of maintaining a sterile cockpit.
He shared the cockpit with a female first officer, 25, who had a total of just 390 hours of flying experience and had never previously landed at Kathmandu as crew, the report said, contradicting a US-Bangla spokesman who last year said she had made landings there before.
Landing at Kathmandu airport, which is surrounded by hills, is considered difficult. In 1992, all 167 on board a Pakistan International Airlines aeroplane were killed when it plowed into a hill as it tried to land.
On the US-Bangla flight, the disparity in experience and added authority of the captain probably deterred the first officer from being more assertive during significant phases such as the final approach and landing, the report said.
The report recommended that the airline emphasise proper crew resource management and set up a mechanism to monitor and assess the mental status of the crew regarding professional development, financial, personal and psychological issues.
Pilot mental health was spotlighted by a 2015 crash in Europe after a Germanwings first officer deliberately flew a jet into a mountainside.
Last year, the European Commission adopted new rules on the mental health of pilots, for the first time requiring airlines to do a psychological assessment before hiring them.
