A Southwest plane started descending too early over Oklahoma City.

The plane’s low altitude triggered an alarm and surprised some residents near Oklahoma City, where it landed safely.

A Southwest Airlines plane descended too early over Oklahoma City on Wednesday, startling residents, before climbing again and landing safely.

After starting its descent from 39,000 feet, Southwest Flight 4069 from Las Vegas to Oklahoma City was still nine miles from the airport when it reached about 525 feet. The plane then climbed to 3,000 feet before landing safely at Will Rogers World Airport at 12:16 a.m.

The Federal Aviation Administration said an automated warning was triggered by the low altitude, and an air traffic controller alerted the pilots.

In a recording from LiveATC.net provided to The Oklahoman newspaper, the controller can be heard saying, “Southwest 4069, low altitude alert. You good out there?”

The F.A.A. said it was investigating the incident.

The plane’s low point occurred over Yukon, just west of Oklahoma City, and some residents reported on social media that they were alarmed by the noise and low flight path.

In a statement, the airline said, “Southwest is following its robust Safety Management System and is in contact with the Federal Aviation Administration to understand and address any irregularities with the aircraft’s approach to the airport.”

There is no sign of mechanical failure causing this incident, but Boeing planes have had several recent safety issues.

In January, a door panel blew out of an Alaska Airlines 737 Max 9 jet, causing some planes to be temporarily grounded, prompting the company to enhance safety measures, and resulting in an apology from the company’s CEO, Dave Calhoun.

Last month, a Southwest Boeing 737 Max 8 flying from Phoenix to Oakland encountered a Dutch roll, where the plane experiences side-to-side and rocking motions simultaneously.