The U.S. Federal Aviation Administration is launching a safety review of Southwest Airlines after a series of near-miss incidents including some that raised serious concerns, the airline said today.

The review prompted by several safety incidents is unusual but in March the FAA said it was initiating a formal evaluation of United Airlines to ensure the Chicago-based carrier was complying with safety regulations and the FAA imposed some restrictions on United.

Southwest confirmed the FAA safety review today and said it is working closely with the agency on its evaluation of recent events. The carrier noted it recently formed a dedicated team of subject-matter experts, leaders, union partners, and the FAA to bolster its existing safety management system.

“This group is tasked with performing an in-depth, data-driven analysis to identify any opportunities for improvement,” Southwest said.

The FAA said on Saturday it was investigating a July 14 Southwest Airlines flight after it flew at a very low altitude over Tampa Bay, Florida. The flight was approximately 4.8 miles from the Tampa airport when it dropped to as low as about 150 feet, according to Flightradar24 data.

The FAA confirmed it had launched the safety evaluation. The FAA has increased oversight of Southwest Airlines to ensure it is complying with federal safety regulations,” the agency said. “Safety will drive the timeline.”

The Tampa flight was the latest in a string of Southwest incidents that have raised safety concerns, including a Southwest 737 flight in April that came within about 400 feet (122 meters) of the ocean off Hawaii after the first officer inadvertently pushed forward on the control column and the plane hit a maximum descent rate of about 4,400 feet per minute.

The FAA is also investigating another very low altitude Southwest flight about 9 miles (14.5 km) from the Oklahoma City, Oklahoma, airport that had departed from Las Vegas dropped to about 500 feet.

The U.S. National Transportation Safety Board and FAA are also investigating a Southwest 737 MAX flight on May 25 that experienced a “Dutch roll” at 34,000 feet while en route from Phoenix, Arizona, to Oakland, California.

Such lateral asymmetric movements are named after a Dutch ice skating technique and can pose serious safety risks.

The agency is also investigating a June 25 Southwest flight that departed from a closed runway in Portland, Maine.