Look closely at this photo. Can you spot the problem?
What's going on here made one passenger seriously furious at his seatmate. So furious that he ended up taking his rage public.
The image, which was uploaded to Reddit by That1one - guy, shows the passenger behind sticking their feet under the seat and well and truly into his space. How is that even possible? They must be really tall, or especially flexible.
He posted it along with the caption: "If you do this during a three hour flight, f*** you."
As if legroom wasn't tight enough already - they definitely weren't toeing the line when it comes to in-flight etiquette.
There were some rather funny responses to the image, with suggested courses of action including:
"Reach down and tie their shoelaces together!"
"Massage their feet while saying 'ooo, what preciouses for golem'"
"Just play footsie with them."
But it turns out that things could be a lot worse. Check out these horrifying snaps that have made their way onto the site Passenger Shaming.