Passengers travelling on American Airlines have reported hearing strange and unexplained moans over the intercom system during flights.
Film producer Emerson Collins captured the strange noises while flying on 6 September from Los Angeles to Dallas, sharing his footage on social media.
The video has since racked up millions of views on Twitter and TikTok.
The noises started before takeoff and persisted while the plane was in the air, Mr Collins told The Washington Post.
In the video, posted on Mr Collins’ social media channels, the sounds range from groans and grumbles to whoops.
"I swear it’s a prank," a flight attendant can be heard explaining to Mr Collins in the video.
At one point, a flight attendant speaks through the intercom and apologises for the "extremely irritating sound", adding that the pilots are working to mitigate the problem.
As soon as she stops speaking, the sounds restart, with one resembling a "ho!" followed by a guttural moan.
Mr Collins apparently walked up and down the aisle, trying to find where the noises were coming from, without success.
"I’m Nancy Drewing my way looking for the person who looks thoroughly amused by themselves," he said. "And, of course, I didn’t see anything."
The Airbus A321 landed safely in Dallas. Mr Collins said he found the incident funny and that the flight crew had reassured passengers there was no need to worry.
"This was fully just a very modern form of immersive in-flight entertainment," he said.
When Mr Collins posted the video, passengers on other American flights came forward reporting the same noises.
"It wasn’t the whole flight, but periodically weird phrases and sounds. Then a huge ‘oh yeah’ when we landed. We thought the pilot left his mic open," Doug Boehner tweeted about his recent Orlando to Dallas flight.
Another Twitter user claimed that he and his wife had experienced a similar phenomenon on an AA flight in July.
"To be clear, it was just sounds like the moans and groans of someone in extreme pain. The crew said that it had happened before, and had no explanation."
A spokesperson for American Airlines told The Independent: “The PA systems onboard our aircraft are hardwired and there is no external access.
“Following the initial report, our maintenance team thoroughly inspected the aircraft and the PA system and determined the sounds were caused by a mechanical issue with the PA amplifier, which raises the volume of the PA system when the engines are running.”
“Our team is reviewing the additional reports,” they added.
