Biman's ageing fleet has been heavily criticised
A Biman Bangladesh airlines flight from Dhaka to London was delayed by nearly 10 hours - because all five of the plane's toilets were blocked.
The airline said staff took two hours to fix the problem, which had been caused by passengers trying to flush away paper cups and other rubbish.
The plane's departure was then further delayed to fit in with a night flight ban at Heathrow airport.
A Biman official said there had been no mechanical fault with the aircraft.
Wing Commander Asaduzzaman, director of engineering at Biman, said most of the passengers on the flight had been Bangladeshis returning to London.
"The flight was delayed because of the toilet jam," he told the BBC.
"Passengers threw bottles, cups, tissue papers and female sanitary napkins into all five toilets of the Biman aircraft.
"This solid material blocked the toilets and there was a jumble in the pneumatic toilet suction system. It was a passenger-created problem. There was no mechanical fault."
Wing Commander Asaduzzaman said the toilets had been fixed two hours after the flight should have taken off at 1400 local time (0700 GMT).
"We could have taken off at 1600 but there is a night ban at Heathrow airport, so we took off at 2330."
Bangladesh's Daily Star newspaper said the flight had been carrying more than 200 passengers.
"It's a fact that the aircraft of the national flag carrier could not fly only because of faults in its toilets," it quoted one of Biman's pilots saying.
The news came a day after reports that the United Nations had advised staff not to fly Biman because of concerns over safety and flight delays.
The cash-strapped airline has been heavily criticised for its performance in recent years.
It has struggled to pay salaries and fuel bills and to maintain its elderly fleet of aircraft. It has also faced a string of corruption allegations.
Biman's managing director, Zakiul Islam, told the Daily Star he was unaware of any UN directive, but admitted the airline was having problems managing its flight schedule.
He hoped things would improve once three Boeing aircraft had been added to Biman's fleet, the paper said.