Officials and the idly curious are asking how a Southwest Airlines Boeing 737 with 129 people on board that took off Sunday from Chicago, bound for Branson, Mo., ended up in a small municipal airport several miles from its destination.

The National Transportation Safety Board, the Federal Aviation Administration, and, not least of all, Southwest Airlines, are asking the same question.

The simple answer is that the pilot put it there.

No one Monday at the NTSB, FAA or Southwest would discuss publicly an incident under investigation, but a person familiar with what happened shared some of the details.

After the plane gained cruising altitude from Chicago, it was under the supervision of an FAA air traffic control center in Kansas City, Mo. Those centers control aircraft when they are at an altitude high enough to create vapor trails. In busy urban areas, such as Washington or any other East Coast airport, a second group of controllers in a facility called a TRACON take over when a plane begins to descend. They hand off to the tower only after the wheels are down, and the plane is on its final approach to land.

A handoff consists of telling the pilot to switch to another radio frequency and contact the next group of controllers.

No TRACON (which stands for Terminal Radar Approach Control Facility) serves relatively rural Branson. So, the center that controls high-altitude flight gave the Southwest plane the correct coordinates for a Branson landing and then handed off directly to the Branson tower.

It’s unclear whether the pilot contacted the Branson tower or just relied on instincts to make a visual landing. In the dark, a brightly lit airport generally is fairly easy to spot.

The pilot had been turned to approach Branson from the south on a compass heading of 014 degrees. M. Graham Clark Downtown Airport, a smaller airport in Hollister, Mo., that handles small private planes, was on a heading of 012 degrees. The Southwest plane would have had to almost fly over it to reach Branson.

“If you didn’t know what your were looking at, you’d see the [Clark] runway lights below and say, ‘Wait, is that our airport?’ ” said the person familiar with the incident who spoke on condition of anonymity because he was not authorized to discuss the investigation. “Instead of making a sweeping left turn, they made an abrupt left and landed.”

Passengers said the pilot hit the brakes hard. The Clark runway is 3,738 feet long, while Branson’s runway is 7,140 feet long. The plane reportedly stopped with about 40 feet to spare, and those bound for Branson were less than nine highway miles from their intended destination.

“A few minutes later, the pilot called to say he’d landed in the wrong place,” the person said.

The pilot and co-pilot have been put on paid leave pending the outcome of the investigation