According to British air accident investigators, the plane, en route to the U.S., departed from London last month with four damaged windows, including two that were completely missing.
No one was harmed due to the window malfunction, which apparently was caused by powerful lighting used during a film shoot, reported the UK Air Accidents Investigation Branch (AAIB) in a special bulletin published on November 4.
The plane took off from London Stansted Airport on the morning of October 4, with 11 crew members and nine passengers on board, all of whom were employees of a "tour company or aircraft operator," according to the report, without specifying the tour firm.
The narrow-bodied Airbus A321 accommodates over 170 passengers, but the small group of passengers was seated in the middle of the cabin, just in front of the wing exits.
According to the AAIB report, the missing windows were not noticed until the plane reached an altitude of 13,000 feet.
"Some passengers recalled that after takeoff, the aircraft cabin seemed noisier and colder than they were accustomed to," investigators wrote. A crew member approached the rear of the plane and noticed a popping window seal on the left side of the aircraft.
"The window pane appeared to have slid down," the report said. "He described the noise in the cabin as 'loud enough to damage your hearing.'"
As the plane approached 14,000 feet, the pilots reduced speed and halted the ascent. An engineer and the second pilot went back to look at the window and agreed that the plane should turn back immediately.
One person died after a Southwest plane with a malfunctioning engine made an emergency landing DUAL-LAYER One person died after a Southwest plane with a malfunctioning engine made an emergency landing The plane safely landed back at Stansted after a total flight time of 36 minutes, during which the aircraft remained "under normal pressure," investigators wrote.
Upon inspecting the aircraft from the ground, the crew found the second window missing and the third one displaced. The fourth window seemed slightly protruded from the frame.
One broken window was later found on the runway during a routine check.
According to the AAIB assessment, the windows could have been damaged by powerful projectors used during filming the day before the flight.
In the photos from the AAIB special bulletin, projectors used during a film shoot a day before the plane's departure from Stansted Airport in London are shown. Air Accidents Investigation Branch Lights designed to create the illusion of a sunrise were positioned approximately 20-30 feet from the aircraft and illuminated the right side and then the left side of the aircraft for a total of over nine hours.
The foam lining melted on at least one of the windows, and several window panes appeared to be deformed due to thermal heating.
"Another level of damage inflicted in the same way could have led to more serious consequences, especially if the window's integrity had been compromised at a higher pressure differential," the AAIB writes. As of the time of NPR's publication, the agency had not responded to a callback.
In 2018, Southwest passenger Jennifer Riordan was fatally injured when she was partially pulled out of a window shattered by shrapnel from an exploding engine.
Since then, several instances of cracked airplane windows have made headlines, but aviation experts claim that the risk of injury or death in such cases is still rare.