Three more Southwest Airlines planes presented small, sub-surface cracks similar to those thought to have caused a hole in the cabin roof of a plane on Friday, officials said. (photo, from bbcimg.co.uk)
While 19 737-300s will return to service as they showed no problems, the National Transportation Safety Board said in a statement that it had been informed by Southwest that “crack indications in the lap joints have been identified on three airplanes they have inspected”.
On Friday a gaping hole in the roof caused a sudden drop in cabin pressure and the Southwest Airlines plane made an emergency landing at a military air base in Arizona.
A section of the 15-year old plane’s ruptured fuselage was removed and sent to NTSB headquarters in Washington for in-depth analysis.
And while conducting inspections of other portions of the lap joint along the fuselage, NTSB investigators found evidence of additional cracks.
‘New and unknown’
Over the weekend the company cancelled 600 flights in order to allow engineers to carry out a special test on 79 of its aircraft.
57 jets still have to be tested, which should be done by Tuesday evening.
Until all jets are back in the air further flight cancellations are expected.
According to the NTSB Boeing will be drafting a “service bulletin” in order to describe the inspection techniques that they would recommend carrying out on similar planes with comparable flight cycles (take-offs and landings) as the one involved in the accident over Arizona.
There are 931 such models in service worldwide, 288 based in the US, but Mike Van de Ven, Southwest’s executive vice-president and chief operating officer said : “What we saw with Flight 812 was a new and unknown issue.”
“Prior to the event regarding Flight 812, we were in compliance with the FAA-mandated and Boeing-recommended structural inspection requirements for that aircraft,” he added.
“We regret any customer inconveniences as a result of the inspections currently under way. Delays and cancellations are never the preference, however we are taking every precaution we can to ensure that our operation is safe.”
In 1988, in an Aloha Airlines plane cracks caused a hole to open over Hawaii, and a flight attendant died in that accident.