It turned into a game of mile-high musical chairs.

The issue of people sitting in the wrong seats on airplanes has become a serious problem. A passenger on a Delta Airlines flight shared a story about how one person sat in the incorrect seat, causing a domino effect of seat changes that disrupted the whole flight.

According to a post now taking-off on Reddit, the high-jinks began after the aisle pirate ignored her ticket — which had her sitting in 30B — and bizarrely opted to sit eight rows back in 37F.

“Perhaps she thought she was on Southwest and had open seating,” quipped the Redditor, referring to the budget airline’s first-come-first-serve seating policy.

Then, instead of confronting her as is the norm, 30B’s rightful occupant chose to relinquish their assigned seat and sit somewhere else.

In turn, the owner of their chair followed suit, igniting a plane-wide “seat shuffle” that eventually resulted in multiple passengers occupying the wrong seats on a completely full flight.

“So the literal last guy on the plane has a window seat and only one middle is left,” recalled the Reddit poster.

Alarmed over this domino effect, flight attendants “started tracking boarding passes” until they located the culprit.

But when they confronted the woman, she “pretended she didn’t know she was in the wrong seat,” per the post.

Reddit commenters were quick to diss the seat squatter.

“These people know what they’re doing. Call them the f–k out,” declared one, while another wrote, “Might be overreacting but I wish she got banned from flying lol.”

However, others blamed the passengers for not calling the woman out. “Look at how many people were unwilling to confront the person in their seat,” wrote one. “Unfortunately this reinforces bad behavior by rewarding it.”

In other words, seat squatting thrives when good people do nothing.

Other Redditors recalled similar instances of how occupying the wrong chair caused things to snowball inflight.

“I saw this happen where a wife and husband switched seats with a guy to sit together (both middle seats, so shouldn’t have been an issue,” but they were all in the wrong seats to begin with,” another user wrote in the comments. “Caused a huge delay on an already delayed flight.”