A team of mechanics put in some overtime yesterday as the National Transportation Safety Board (NTSB) investigation into the mid-air fuselage rupture of a Southwest Airline plane got underway.

Under the supervision of NTSB inspectors, technicians removed the damaged section of the fuselage skin from the Boeing 737, Southwest Flight #812, that developed trouble in-flight on Friday. The plane safely made an emergency landing in Yuma, Arizona.

The NTSB sent a “Go Team” to Yuma to look into the incident, although the section of fuselage with the hole in it will transported to NTSB headquarters in Washington, D.C. for in-depth analysis.

In addition, NTSB investigators are conducting additional inspections of other portions of the lap joint along the fuselage of the accident airplane and found evidence of additional cracks.

Southwest Airlines has been conducting additional non destructive testing inspections of its own, on several of the company’s 737 airplanes. The NTSB says Southwest has notified the agency that additional crack indications in the lap joints have been identified on 3 airplanes they have 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,” according to a statement. “As a result of the findings from our investigation to date and the results of the Southwest Airlines inspections, 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.” The NTSB says the focus right now is on requiring inspections of the left and right lap joints on all similar 737 airplanes that have comparable cycles (takeoffs and landings) as the accident airplane. “Once the Service Bulletin is released by Boeing, the FAA will make a determination whether to make it mandatory for all similar 737 airplanes.”