It had all the makings of a modern-day airport nightmare: a 13-hour delay, more than 100 cranky and exhausted passengers, and babies running out of formula and diapers.

And that was before an airport employee punched an infant-carrying customer in the face.

A photo of the latest case of air-travel misery shows the exact moment the frustrations of easyJet Flight 2122 boiled over: the outstretched arm of a uniformed airport worker connecting with a man’s cheek, inches away from a baby.

The man who was struck was one of the passengers scheduled to depart from Nice, France, late Sunday morning. The plane was to land at Luton Airport, just outside of London, two hours later. Instead, a mechanical problem with the plane caused a half-day delay.

Worse, said another passenger, Arabella Arkwright, easyJet personnel either didn’t have answers or didn’t communicate them to the passengers languishing in the waiting area. Employees distributed food vouchers, but they barely covered the cost of a muffin at a nearby Starbucks, Arkwright said.

As the hours ticked by, the stranded passengers could hear calls for other easyJet flights that were going to Luton Airport.

It reached a boiling point at the 13-hour mark, sometime before midnight. Passengers were finally told that they could board, then there was a delay at the aircraft’s door, Arkwright said. They were stuck on a skybridge for a half-hour before trudging back into the airport.

A man holding a baby and a cellphone approached an employee for Samsic, a contractor that assists customers at the airport, for more information.

Voices were raised.

Passengers stared.

“It was just the straw that broke the camel’s back,” Arkwright said Monday. “The easyJet employee lifted his hand first and pushed the mobile phone out of the man’s hand. You could see it go flying. The man pushed him back, like he was protecting the baby.”

“And then the (worker) just whacked him,” said Arkwright, who captured the punch on her smartphone camera, then tweeted the photo at British media outlets and the budget airline.

Arkwright said she and other passengers were outraged, but not entirely surprised that the situation had devolved to violence.

Afterward, the airline went into damage-control mode. The puncher, easyJet said in a statement, was not one of their employees. He worked for “special assistance provider” Samsic. The airline said it was trying to get to the bottom of the situation.

Samsic did not return a message seeking comment.

It’s unclear what happened to the worker. Both he and the man he’d punched were escorted away by airport security guards.

The man with the baby returned to the airport with a fresh welt on his face and received applause from the other passengers, who were now seated and ready to take off, according to Arkwright.