April 4, 2011 - The National Transportation Safety Board is investigating an in-flight fuselage rupture that occurred on Friday evening on a Southwest Airline, Flight 812, Boeing 737 aircraft (N632SW). The damaged airplane diverted and landed safely in Yuma, Arizona. 

Southwest Airlines is working with the National Transportation Safety Board (NTSB) to determine the cause of the rupture which leaded to a rapid depressurization of the aircraft.  

Further, the carrier has decided to keep a subset of its Boeing 737 fleet out of the flying schedule to begin an aggressive inspection effort in cooperation with Boeing engineers.  

"The safety of our Customers and Employees is our primary concern, and we are grateful there were no serious injuries," said Mike Van de Ven, Southwest's executive vice president and chief operating officer.  "We have launched personnel to Yuma to begin the investigation process with the NTSB, FAA, and appropriate parties to determine the cause of the depressurization."

The 118 passengers on board Flight 812 have received a full refund along with an apology and two complimentary roundtrip passes on Southwest for future flights.  Preliminary reports indicated the aircraft lost pressure and oxygen masks were deployed shortly after takeoff from Phoenix. After the plane landed safely in Yuma, the crew confirmed a hole in the top of the aircraft, approximately mid-cabin.  

One flight attendant was treated at the scene for a minor injury, as was at least one passenger. No injuries required transport to the hospital. The Company arranged for a Southwest Airlines aircraft to transport the Customers on Flight 812 from Yuma to Sacramento last night. 

As of 4 p.m. Central time Sunday, 19 planes had undergone the intense inspection with no findings, and those planes have been returned to service. In two other airplanes, the testing did detect small, subsurface cracks. Further evaluation and potential repairs will be necessary before those planes are returned to service. Inspections of the remaining aircraft in the sub-fleet (79 total) will continue for the next few days. As inspections are completed with no findings, those planes will continue to be put back into service.  

The airline anticipates completing the inspections by late Tuesday. The 79 aircraft designated for the additional inspections were designed differently in the manufacturing process. On Sunday, Southwest had cancelled approximately 300 flights while the inspections are ongoing.  

"I could not be more proud of our Maintenance and Engineering professionals who supported Boeing and the FAA in the establishment of these new inspection procedures," said Mike Van de Ven, Southwest's Executive Vice President and Chief Operating Officer. "Boeing has since identified an inspection program for this section of the aircraft. Based on this incident and the additional findings, we expect further action from Boeing and the FAA for operators of the 737-300 fleet worldwide."  

Southwest operates a total 737 fleet of 548 planes. The fleet is constantly undergoing rigorous checks and inspections as directed by the FAA and Boeing, the aircraft manufacturer. These checks and inspections are dictated by number of cycles (a cycle is a takeoff and landing) and on a calendar basis as well.  

"Our highest priority is the safety of our Employees and Customers," Van de Ven said. "Prior to the event regarding Flight 812, we were in compliance with the FAA-mandated and Boeing-recommended structural inspection requirements for that aircraft.

?What we saw with Flight 812 was a new and unknown issue. We regret any Customer inconveniences as a result of the inspections currently underway. Delays and cancelations are never the preference, however we are taking every precaution we can to ensure that our operation is safe."

Mechanics from Southwest Airlines, under the supervision of NTSB investigators, removed a section of the ruptured fuselage skin. The segment has be transported to NTSB headquarters in Washington, D.C. for in-depth analysis. 

In cooperation with Boeing, an additional inspection program was set up by Southwest for a subset of the Southwest 737-300. The inspection involved a non-destructive test (NDT) in the form of High-Frequency Eddy current of the aircraft skin. This test is designed to detect any subsurface fatigue in the skin that is not visible to the eye.

In addition, NTSB investigators conducted additional inspections of other portions of the lap joint along the fuselage of the accident airplane and found evidence of additional cracks. The past few days, Southwest Airlines has been conducting additional non destructive testing inspections on several of their 737 airplanes. The NTSB has been informed that additional crack indications in the lap joints have been identified on 3 airplanes that have been inspected. 

The NTSB, along with the other investigative parties - FAA, Boeing, and Southwest Airlines - has been working to determine what actions might be necessary to inspect any similar airplanes. As a result of the initial findings, Boeing has indicated that they will be drafting a Service Bulletin to describe the inspection techniques that they would recommend be accomplished on similar airplanes.