A Southwest Airlines Boeing 737 Max experienced a dangerous 'Dutch roll' mid-flight, likely due to damage from a storm after routine maintenance, leading to substantial tail damage. The plane was parked during severe thunderstorms in New Orleans, with gusting winds up to 84 mph. Following scheduled maintenance, pilots observed rudder pedal movements, indicating potential storm-related damage. Modern planes have safeguards like 'yaw dampers' to mitigate Dutch roll. Investigators are examining fractures in the rudder system and metal components connecting to a power control unit, with no definitive timeline on when the damage occurred.