The Delta pilot had to land after cabin pressure rapidly dropped inside the Heathrow flight to Atlanta, and pulled on his oxygen mask for the descent, a report said.
But the lenses were broken and he couldn’t see properly, and two passenger masks also failed to deploy.
A newly-published report into the August 2017 drama revealed how a rapid rise in pressure sparked an emergency in the air over London.
One flyer fainted as the flight was deliberately plunged into a dramatic descent, the Air Accidents Investigation Branch report said.
It added: “The commander reported that the lenses in his oxygen mask were in poor condition, which affected his visibility, whereas the lenses in the masks of the co-pilot and relief pilot were clear.
“During the emergency, the cabin crew informed the flight crew that all but two of the passenger oxygen masks had automatically deployed and that a passenger had fainted and was being attended by a passenger with a medical background.”
The fuel-laden flight, containing 219 passengers and crew, made its emergency landing at Heathrow despite being ten tonnes overweight.
The cause of the cabin pressure loss could not be identified.
The report added: “The aircraft manufacturer was unaware of any other occasions when the masks had failed to deploy on a Boeing 767 aircraft.
“Should some of the passenger oxygen masks not automatically deploy, then the cabin crew can provide the affected passengers with portable oxygen or mechanically release the oxygen masks.”
Mickleach.com is your news, entertainment, music & fashion website. We provide you with the latest news and videos straight from the entertainment industry.