NTSB Finds Damaged Southwest 737 MAX Flew 44 Times Before Midair Dutch Roll

A Southwest Airlines Boeing 737 MAX 8 that experienced a severe midair wobble in May 2024 flew 44 passenger flights with undetected structural damage before the incident. The National Transportation Safety Board released its final report on Thursday, tracing the failure to an 84-mph thunderstorm that battered the parked aircraft in New Orleans nine days earlier.[1][3][5]

The investigation into Flight 746 highlights how extreme weather on the ground can quietly compromise an aircraft's flight controls. Investigators found that the storm damaged the ribs inside the vertical stabilizer where a backup rudder control unit is mounted. Neither Boeing’s maintenance manuals nor Southwest’s internal procedures triggered an inspection before the jet returned to service.[2][4][6]

"The probable cause was damage to the standby rudder power control unit connection to the vertical fin due to an extreme high wind event while the airplane was parked," the NTSB wrote in its final report. The agency noted that the damage "remained undetected and resulted in anomalous operation" of the system.[3][7]

The incident culminated on May 25, 2024, as the aircraft cruised at 34,000 feet from Phoenix to Oakland. The captain reported feeling "a small amount of Dutch roll," a coupled motion where the plane's nose yaws side to side while the wings rock up and down. All 175 passengers and six crew members landed safely.[3][4][8]

A Storm and a Missed Threshold

The sequence of missed opportunities began on the night of May 16, 2024. The aircraft, registered as N8825Q, sat parked on a remote stand at Louis Armstrong New Orleans International Airport. A squall line passed through the area under a tornado watch, bringing wind gusts that peaked at 73 knots.[2][3][5]

Because the 737's rudder lacks a gust lock, the wind slammed the control surface hard enough to fracture a structural rib with signs of overload. At the time, Boeing’s maintenance manual required a special inspection following extreme winds, but it did not specify a numerical wind speed threshold that would mandate the check.[1][4][6]

Without a hard number to trigger a maintenance alert, Southwest Airlines had no formal process to notify its mechanics when a parked plane endured severe weather. The aircraft was cleared for flight the next morning and completed 38 uneventful legs over the following week, carrying thousands of passengers with a compromised tail structure.[2][4][7]

A crucial opportunity to detect the damage arrived on May 23 during a scheduled maintenance check in Houston. Mechanics performed a test of the standby hydraulic system, which requires a technician to stand at the tail and visually confirm that the rudder swings fully to both the left and the right.[1][3][8]

The Failed Hangar Test

Southwest maintenance records show the hydraulic test was signed off as passed. However, the NTSB reviewed hangar security video that showed the rudder moving to the right but failing to travel to the left. Investigators noted that no mechanic was actually positioned at the rear of the aircraft to watch the movement.[2][3][5]

The aircraft returned to service despite the flawed test. On its fourth flight the following day, a flight crew disconnected the yaw damper—a system that automatically stabilizes the rudder—after reporting that it felt like it was overcorrecting in turbulence. The system was deferred, tested, and returned to service just before the Oakland flight.[1][2][6]

Flight data from the incident flight showed rudder oscillations of about 0.75 degrees in both directions, occurring in bursts that lasted roughly 20 seconds. The NTSB determined that the damaged mounting bracket caused the standby rudder power control unit to operate abnormally whenever the yaw damper was engaged.[3][4][7]

The NTSB classified the structural failure as substantial damage, officially elevating the event from an incident to an accident. The agency explicitly tied the failure to the undetected storm damage and the subsequent maintenance lapses, rather than citing any fundamental design defect in the Boeing 737 MAX rudder system itself.[3][4][8]

AI

Closing the Procedural Gaps

In the wake of the findings, both the manufacturer and the airline have overhauled their procedures to prevent a recurrence. Boeing revised its 737 maintenance manual in May 2025 to establish a firm threshold, requiring a special high-wind inspection anytime an aircraft is exposed to gusts of 65 knots or 75 mph.[1][2][5]

The new 65-knot threshold sits comfortably below the 73-knot gusts that battered the Southwest jet in New Orleans. Under the revised rules, that storm would have automatically grounded the aircraft for a structural inspection before its first flight the next morning, closing the gap that allowed the damage to slip through.[3][4][6]

Southwest Airlines immediately inspected the rudder control unit mountings across its entire fleet of 231 Boeing 737 MAX aircraft and found no similar damage. The carrier also implemented a new automated weather monitoring process to immediately alert maintenance control whenever a parked aircraft is exposed to extreme wind events.[1][2][7]

To address the hangar oversight, Southwest replaced its previous one-line instruction for the standby hydraulic test with a detailed, step-by-step work card. The new protocol requires individual mechanics to physically sign off on each specific step, ensuring someone is always positioned to verify the rudder's full range of motion.[1][3][8]

The resolution of the Flight 746 investigation underscores how modern aviation safety relies heavily on procedural redundancies. When a physical component fails, the system depends on maintenance thresholds and visual inspections to catch the issue before the aircraft ever leaves the ground.[2][4][5]

By quantifying the exact wind speed that demands an inspection, the industry has removed the ambiguity that left the New Orleans storm unflagged. The NTSB's final report serves as a definitive roadmap for how airlines must monitor their fleets even when the engines are shut down and the planes are empty.[3][4][6]