“A major catastrophe was avoided by feet,” said safety expert Steve Arroyo, who landed on that same short runway many times during his career at United. “Had it been another five feet lower, eight feet, I mean, no more than 10 feet, that plane would have been all over the New Jersey Turnpike.”

The driver of the bakery delivery truck was treated at a hospital for minor injuries, and the Boeing 767 flying in from Venice, Italy, with 231 people aboard was able to land safely. No one on the plane was hurt. Air traffic control audio suggests the incident may have created a hole in the side of the plane, but the airline and the National Transportation Safety Board haven’t confirmed that.

The NTSB said Monday afternoon that it has reclassified the incident as an accident because of the extent of the damage to the plane, but it didn’t provide any details.

Anyone who drives that section of Interstate 95 near the airport is likely used to seeing planes coming in low and crossing over all the lanes of traffic as the planes get ready to land, but never this low. Dash camera video from inside the truck shows the moment of impact and appears to show the truck toppling onto its side. Typically, semitrucks are 13.5 feet (4.1 meters) tall, so the plane was quite low.

The pilots’ damage report wasn’t recorded because the crew opted to call the tower on the phone after landing instead of broadcasting the details over the radio.

But air traffic control audio posted by ATC.com revealed a discussion between an air traffic controller and a ground vehicle more than half an hour after the incident. “They felt something over the threshold and there’s a hole in the side of the airplane,” the controller said.

NTSB investigators arrived on scene on Monday to interview the flight crew and begin working to figure out how and why this happened. But the NTSB may not offer many details about what happened until it publishes its preliminary report roughly a month from now. The agency does not plan any news conferences on this accident.

Runway 29, where the plane landed, is the shortest runway at the airport at 6,726 feet (2,050 meters), and it is generally only used when there are strong winds like there were on Sunday afternoon. The other two Newark runways are 11,000 feet (3,353 meters) long. An air traffic controller told pilots at the time that the winds were gusting up to 31 mph (50 kph).

Arroyo said that investigators will definitely look at how well the United crew planned for the contingency that they would have to land on Runway 29 and exactly what data they had entered into their flight control system and navigational aids in the cockpit. He said those systems can help keep pilots on track in the glidepath before they have to take the controls and complete the landing visually.

“It’s one of the most challenging approaches in the world,” Arroyo said. “The margin of error is extremely low.”

Jeff Guzzetti, a former crash investigator for the NTSB and the Federal Aviation Administration, said he can’t think of another accident when an airliner has struck a vehicle. It has happened with small planes before, but not airline jets. He said that investigators will likely also look at whether fatigue could have been a factor after the long flight from Italy.

The NTSB directed United to preserve the cockpit voice and flight data recorders for investigators to examine. The airline said the pilots have been put on leave while the accident is investigated.