WASHINGTON >> The Federal Aviation Administration (FAA) said today it is investigating a Southwest Airlines flight that descended to a low altitude 9 miles (14.5 km) from the Oklahoma City airport.

The incident involving Southwest Airlines Flight 4069, which had departed from Las Vegas, occurred around at 12:05 a.m. Wednesday, the FAA said. After the automated Minimum Safe Altitude Warning sounded, an air traffic controller alerted the flight crew.

Southwest said it is following its Safety Management System and is in contact with the FAA to “understand and address any irregularities with the aircraft’s approach to the airport.”

Several incidents involving Southwest flights in recent months have raised concerns.

Asked on Monday if the incidents would prompt the agency to boost scrutiny of Southwest, as it has with United Airlines , FAA Administrator Mike Whitaker declined to comment. He said the agency reviewed all airline incidents and closely monitored carriers.

“The airline oversight model is a pretty good model that we want to build out for other players in the system,” Whitaker said.

Last week, the FAA and the U.S. National Transportation Safety Board said they were investigating a May 25 Southwest flight of a Boeing 737 MAX. The NTSB said the plane experienced a “Dutch roll” at 34,000 feet while en route from Phoenix, to Oakland, California. Such lateral asymmetric movements are named after a Dutch ice-skating technique and can pose serious safety risks.

The FAA said last week it was also investigating a Southwest 737 MAX 8 flight in April that came within about 400 feet of the ocean off the coast of Hawaii after bad weather conditions prompted pilots to bypass a landing attempt at Lihue airport, on the island of Kauai.

During the go-around, the first officer “inadvertently pushed forward on the control column while following thrust lever movement commanded by the autothrottle,” according to a June 7 airline memo, and the plane began to descend rapidly, hitting a maximum descent rate of about 4,400 feet per minute.

The pilots in a post-debrief said seeing the severity of the flight “through the animations was a significant, emotional event,” the Southwest memo said, adding the airline is reviewing data and trends related to its procedures, training, standards, and performance.