Inspectors have found small, subsurface cracks in three more Southwest Airlines planes that are similar to those suspected of causing a jetliner to lose pressure and make a harrowing emergency landing in Arizona, a federal investigator said.
Southwest said Sunday in a statement that two of its Boeing 737-300s had cracks and will be evaluated and repaired before they are returned to service. A National Transportation Safety Board member told The Associated Press later Sunday that a third plane had been found with cracks developing.
The cracks found in the three planes developed in two lines of riveted joints that run the length of the aircraft.
Nineteen other Boeing 737-300 planes inspected using a special test developed by the manufacturer showed no problems and will be returned to service. Checks on nearly 60 other jets are expected to be completed by late Tuesday, the airline said.
That means flight cancelations will likely continue until the planes are back in the air. About 600 flights in all were canceled over the weekend after Southwest grounded 79 of its planes.
NTSB board member Robert Sumwalt said Boeing was developing a “service bulletin” for all 737-300 models with comparable flight cycle time as the Arizona jet, which was 15 years old and had about 39,000 takeoff and landing cycles.
There are 931 such models in service worldwide, 288 of which are in the U.S. fleet.
Boeing’s bulletin would strongly suggest extensive checks of two lines of “lap joints” that run the length of the fuselage. The NTSB has not mandated the checks, but Sumwalt said the FAA is likely to make them mandatory.
Friday’s flight carrying 118 people rapidly lost cabin pressure after the plane’s fuselage ruptured — causing a 5-foot-long tear (1.5-meters) — just after takeoff from Phoenix.
Passengers recalled tense minutes after the hole ruptured overhead with a blast and they fumbled frantically for oxygen masks. Pilots made a controlled descent from 34,400 feet (10,485 meters) into a southwestern Arizona military base. No one was seriously injured.
The tear along a riveted “lap joint” near the roof of the Boeing 737 above the midsection shows evidence of extensive cracking that hadn’t been discovered during routine maintenance before the flight — and probably wouldn’t have been unless mechanics specifically looked for it — officials said.
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