Inspectors find cracks in jet
St Petersburg - US safety inspectors have found evidence of "widespread cracking" and fatigue on the fuselage of a Southwest Airlines Boeing 737 that made an emergency landing in Arizona with a hole in the cabin on Friday.
National Transportation Safety Board Member Robert Sumwalt said at a media conference on Sunday: "Was the aircraft well maintained and should it have been maintained better?
"That is exactly why we are here...to see why this problem has occurred."
As a result of the incident, Southwest has grounded part of its fleet for inspections.
The airline cancelled 300 flights on Saturday and said it expected to cancel another 300 flights on Sunday as the investigation continued into what caused the hole to develop during Southwest Flight 812 on Friday.
The flight from Phoenix to Sacramento landed at a military base in Yuma, Arizona, after the hole appeared suddenly at about mid-cabin.
The cancellations are likely to continue for the next few days, Southwest Airlines spokesperson Whitney Eichinger said.
Airline mechanics will saw out the portion of the plane skin that fractured and it will be flown to Washington for further inspection, Sumwalt said.
"We did find evidence of widespread cracking across this entire fracture surface," said Sumwalt.
But determining exactly where the cracks are is "a very involved process," he said.
Recorders from Flight 812 arrived at NTSB's headquarters on Saturday night.
They indicated that the decompression occurred approximately 18 minutes after takeoff, Sumwalt said.
The flight crew donned oxygen masks and declared an emergency.
The plane descended from its cruising altitude of 10 970m to 3 350m in just over 4 minutes, Sumwalt said.
A total of 931 Boeing 737-300s are operated by all airlines worldwide, with 288 of them in the United States, the Federal Aviation Administration said earlier.