Federal officials said Thursday they’re investigating an unusual rolling motion on a Southwest Airlines Boeing 737 Max 8 that might have been caused by a damaged backup power-control unit.

The Federal Aviation Administration said it’s working with Boeing and the National Transportation Safety Board to investigate the incident on a May 25 flight from Phoenix to Oakland. Southwest says it’s working with the FAA and Boeing.

The FAA said the plane went into a “Dutch roll,” the name given to the combination of a yawing motion when the tail slides and the plane rocks from wingtip to wingtip — a motion said to mimic the movement of a Dutch ice skater.

Updated information provided by the NTSB on Friday said it happened when the jetliner was at about 34,000 feet.

https://www.cbsnews.com/news/southwest-airlines-dutch-roll-boeing-737-max-phoenix-oakland-flight/