The Boeing 737-300 was en route from Phoenix to Sacramento, Calif., on April 1, 2011, when a 5-foot-long gash opened in the fuselage. Air rushed in, oxygen masks dropped from the ceiling and a flight attendant fainted, breaking his nose, as the pilots made a rapid descent and an emergency landing at Yuma International Airport.
The NTSB's findings, released Friday and first reported by The Seattle Times, say that when the jet was assembled in 1996, two panels appeared to have been misaligned, and many rivet holes were drilled incorrectly. The agency said it showed "a lack of attention to detail and extremely poor manufacturing technique."
Hidden cracks began emanating from the rivet holes soon after the plane entered service and had been growing slowly ever since, the NTSB said.
It isn't clear whether the work was done at initial fuselage assembly at Boeing's plant in Wichita, Kan., which is now Spirit AeroSystems, or during final assembly in Renton, Wash., the report said. At the time, Boeing only kept manufacturing records for up to seven years.
In an emailed statement Saturday, Boeing said it's dedicated to the safety of its planes and that it provided technical assistance to the NTSB investigators. The company pointed out that inspections on other 737s found no similar damage — suggesting the problem was isolated.
The NTSB said it couldn't determine why Boeing's quality-assurance protocols failed to discover the shoddy work, but concluded that in light of the one-off nature of the problem, it is "unlikely that there was a systemic (quality assurance) error at the Boeing facilities."
The NTSB report also addressed the injury suffered by the flight attendant, who told investigators that despite being trained to put on his oxygen mask immediately, he thought he "could get a lot more done" before putting on the mask. Instead, he tried to make a call or a public announcement to the passengers first, quickly passed out and broke his nose.
An off-duty airline employee flying as a passenger passed out while trying to help the flight attendant and suffered a cut above his eye.
The NTSB report notes that people can lose consciousness in as little as six seconds in the event of a rapid de-pressurization of an airplane cabin.
At the time, the incident raised questions about whether aging jets might be more susceptible to metal fatigue earlier than previously thought. But Hans Weber, an aviation technical expert, president of Tecop International in San Diego, told The Seattle Times that the NTSB analysis dispels that concern.
"The workmanship was just terrible," Weber said. "This has nothing to do with a typical fatigue fracture due to aging."