Another security scare hit O’Hare International Airport this weekend — this time involving a delivery driver who drove into unauthorized secured areas before someone caught on.

His explanation might be a shock.

Travelers at O’Hare are likely familiar with the sight of cars coming through to pick up and drop off passengers. Anyone caught stopping for too long is told to keep it moving.

The tight ship run at pickup and drop-off makes what happened around noon Saturday highly confusing. A DoorDash driver drove through secured areas before someone realized he wasn’t supposed to be there.

A source told CBS News Chicago the delivery driver drove miles along the interior and restricted roads at O’Hare — potentially crossing runways — before someone spotted him from the air traffic control tower.

“I was just going to say, another one, yeah,” said business jet pilot and former air traffic controller Robert Mark.

Mark said such incidents are a huge safety concern. He was asked how often they happen.

“Luckily, not very often — but I have seen it, at other airports, and it’s frightening when you’re up, and then you go, ‘Who the heck is that?'” Mark said.

Chicago police confirmed a 36-year-old man was working as a delivery driver when he “accidentally drove into an unauthorized secured area within O’Hare Airport.”

Police added that they conducted a preliminary investigation and deemed the delivery driver’s actions a mistake, and no charges or citations were filed.

“But now imagine if this had been at night in the darkness, I mean, where no one noticed this person,” said Mark. “Headlights all look the same pretty much in the dark. This could have been really, really bad.”

The company said it is looking into the incident.