07:24 AM EDT, 07/10/2024 (MT Newswires) -- A Southwest Airlines ( LUV ) Boeing Max 737-8 plane that experienced an unusual rolling motion several times during a flight on May 25 had undergone scheduled maintenance two days earlier, The National Transportation Safety Board said on Tuesday.

Following the May 25 incident, Southwest ( LUV ) technicians discovered structural damage to the plane's rudder system. In addition, the maintenance crew found damage to a backup system that aids in controlling rudder movement, which is a part of the aircraft that had successfully passed tests following the May 23 maintenance work.

Flight 746 experienced a so-called Dutch roll when the plane's tail rocks side to side. Initially, pilots suspected turbulence but later discovered unusual rudder pedal movement, the report said.

Post-landing inspections revealed damage near the plane's tail, which according to the NTSB, "adversely affects the structural strength of the fitting and is considered substantial damage."

The Federal Aviation Administration launched a separate investigation into the May 25 event.

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