The Federal Aviation Administration is investigating an in-flight incident on a Southwest Airlines Boeing 737 MAX 8 jet that departed from Phoenix Sky Harbor International Airport.

On May 25 while en route to Oakland, California, Southwest flight WN746 experienced a phenomenon known as a Dutch roll, the plane was taken out of service and flown to Paine Field in Everett, Washington where it’s being investigated.

No one on board was killed or injured, though the FAA noticed “substantial” damage to the plane in its initial investigation.

It’s the latest incident involving a Boeing plane. The Boeing 737 MAX 9 was grounded for about three weeks after a door plug malfunction blew a hole in an Alaska Airlines MAX 9 in January.

Here’s what to know about the incident and the investigation, including what a Dutch roll is.

Online passport renewal: Here’s who can and can’t do it

What happened on the Phoenix-Oakland Southwest flight?

On May 25, while en route from Phoenix to Oakland on Southwest Flight WN746, the aircraft experienced a phenomenon known as a Dutch roll, when a plane rocks from side to side while its tail yaws, or “wags,” making it difficult for the pilot to maintain control of the plane.

The pilot regained control of the plane and no one on board was harmed. The Boeing 737 MAX 8 landed in Oakland safely. A post-flight inspection revealed damage to the plane’s standby power control unit.

The Boeing 737 MAX 8 involved in the incident, which FAA records show was certified on Dec. 19, 2022, was grounded after the flight. FlightAware data for the plane showed it last flew on June 6, traveling from Oakland to Boeing’s assembly plant at Paine Field in Everett, Washington.

What is a Dutch roll?

A Dutch roll is a combination of side-to-side rocking motions with “tail-wagging,” or yaw. Yaw is defined as rotation around the vertical axis of the plane.

It happens when a plane’s lateral stability, or its ability to resist rolling, is greater than directional stability, or its ability to stay pointed straight, said Dinuwan Galwatta, an aeronautical engineer who shares his expertise on his TikTok channel, The Aero Technician.

He said there are three methods used to manage the impact of a Dutch roll:

• Aeronautical engineers design aircraft to achieve a balance between lateral and directional stability. Wing design, vertical stabilizer size, and even control systems all play a role.

• In some situations, pilots can use rudder inputs to dampen the Dutch roll by anticipating the roll and countering it with small rudder corrections.

• Modern aircraft often have yaw dampers, which are automatic control systems that use small rudder movements to actively suppress Dutch roll.

What is Southwest Airlines saying about the MAX 8 incident?

Southwest Airlines told The Arizona Republic that they’re in contact with the FAA and Boeing regarding the incident, and declined further comment.

Other Boeing 737 MAX 8 incidents

The Dutch roll that occurred on the Southwest Airlines flight from Phoenix is the latest incident involving the Boeing 737 MAX 8. Here are others:

• October 2018: A Boeing 737 MAX 8 operated by Indonesia’s Lion Air plunged into the Java Sea, killing all 189 people on board. The investigation, completed in 2021, blamed the crash on a faulty angle of attack sensor on the plane that fed pilots inaccurate data.

• March 2019: An Ethiopian Airlines 737 MAX 8 crashed about six minutes after takeoff, killing all 157 people on board. Ethiopian investigators issued their final report on the crash in 2023, blaming electrical issues that led to the activation of the plane’s Maneuvering Characteristics Augmentation System.

• April 2021: Months after the 737 MAX 8 was recertified by the Federal Aviation Administration, Boeing flagged a potential electrical issue and airlines temporarily took the plane out of service. The FAA approved a fix for the issue a month later.

• February 2024: A United Airlines flight from Nassau, Bahamas, to Newark, New Jersey, experienced “stuck” rudder pedals on its landing roll. None of the 161 people on board were injured. Months before the incident, Boeing advised airlines to inspect their 737 MAX planes for a possible loose bolt in the rudder control system. The National Transportation Safety Board is investigating.

• March 2024: Another United Boeing 737 MAX 8 slid off the runway into the grass upon landing at Houston George Bush Intercontinental Airport. None of the 166 people on board were injured. The NTSB is investigating.

Michael Salerno is an award-winning journalist who’s covered travel and tourism since 2014. His work as The Arizona Republic’s consumer travel reporter aims to help readers navigate the stresses of traveling and get the best value for their money on their vacations. He can be reached at Michael.Salerno@gannett.com. Follow him on X, formerly Twitter: @salerno_phx.

Support local journalism. Subscribe to azcentral.com today.

This article originally appeared on Arizona Republic: Southwest Airlines Boeing 737 MAX 8 grounded after ‘Dutch roll’