WASHINGTON, June 20 (Reuters) -

The Federal Aviation Administration (FAA) said on Thursday

it is investigating a Southwest Airlines ( LUV ) 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 ( LUV ) 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 ( LUV ) flights in recent

months have raised concerns.

Asked on Monday if the incidents would prompt the agency

to boost scrutiny of Southwest ( LUV ), 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 ( LUV )

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 ( LUV ) 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 ( LUV ) memo said, adding the airline is reviewing

data and trends related to its procedures, training, standards,

and performance.