Officials to order inspections for 737s

PHOENIX -- Federal aviation officials late Monday readied an order for emergency inspections on 80 U.S.-registered Boeing 737 jetliners such as the one on which a piece of fuselage tore away more than 30,000 feet above Arizona last week.

The order, to be issued to day, is directed at finding weaknesses in the metal in the fuselage. Nearly all of the affected aircraft already will have been inspected by the time the order takes effect.

Southwest's schedule largely has returned to normal at McCarran International Airport. Southwest, the largest carrier into Las Vegas, canceled 27 of the 232 scheduled departures on Sunday, according to flightstats.com. By Monday, cancellations had dropped to seven out of 243 flights, with only two coming after 7 a.m.

A 5-foot-long hole opened up in the roof of the Southwest Airlines plane soon after takeoff Friday from Phoenix, causing a loss of pressure and forcing pilots to make an emergency landing 125 miles to the southwest in Yuma, Ariz. No one was seriously hurt.

The safety directive applies to about 175 aircraft worldwide, including 80 planes registered in the United States, the Federal Aviation Administration said. Of those 80, nearly all are operated by Southwest. Two belong to Alaska Airlines.

A popular plane with the airlines, 289 of the 481 daily flights out of McCarran are 737s. But only Southwest flies the 300 model. Delta, the No. 2 airline at McCarran, does not have any 300s in its fleet.

Southwest, which operates 181 Boeing 737-300 jets in a fleet of 548, owns one of the largest fleets of the airplane, with International Lease Finance Corp. and Ireland's GPA Group, MarketWatch reported for a story on its website. United Airlines, now a part of United Continental Holdings Inc. and also a major carrier at McCarran, grounded its 737-300 fleet at the end of 2009.

After the midair incident, Southwest grounded nearly 80 Boeing 737-300s for inspections. By Monday evening, 64 were cleared to return to the skies, and three were found with cracks similar to those found on the Arizona plane.

Friday's incident raised questions about the effects that frequent takeoffs and landings by short-haul carriers such as Southwest put on their aircraft and the adequacy of the inspections.

Because there had been no previous accidents or major incidents involving metal fatigue in that spot of the fuselage, Boeing maintenance procedures called only for a visual inspection by airlines.

But airlines, manufacturers and federal regulators have known since at least 1988 that planes can suffer microscopic fractures. That year, an 18-foot section of the upper cabin of an Aloha Airlines 737-200 separated in flight, sucking out a flight attendant.

The order is "certainly a step in the right direction," said National Transportation Safety Board member Robert Sumwalt, who is in Yuma with the board's accident investigation team.

The FAA's emergency order will require initial inspections using electromagnetic devices on some Boeing 737 aircraft in the -300, -400 and -500 series that have accumulated more than 30,000 takeoffs and landings, the agency said. It then will require repetitive inspections at regular intervals.

The inspections mark at least the second time that Southwest has had to contend with fuselage cracks. In July 2009, the Dallas-based airline inspected all of its 737-300 jets after a 1-foot hole opened up at the top of its fuselage in midflight, MarketWatch reported on its website.

Southwest's jet was 15 years old and had logged 39,000 pressurization cycles, a measurement of the number of takeoffs and landings. That is 7.2 cycles every day for every year it has been in service.

Boeing said Monday that it will issue guidance this week on how airlines should do checks on the affected airplanes now in service. An estimated 1,800 airplanes, including -300, -400, -500 model 737s, are affected by the aircraft maker's service bulletin.

The problem of what is known as "widespread fatigue damage" in aging planes has a long, well-documented history.

It became a safety focus of the FAA and was the subject of congressional hearings after the Aloha Airlines incident. The NTSB cited such fatigue damage as a contributor to that accident.

Widespread fatigue damage is characterized not only by visible cracks but also microscopic, subsurface fractures that aren't visible and had been going unnoticed in inspections.

After the Aloha accident, FAA instituted a new safety regime for older 737s for cracking that includes not only visual inspections but the use of devices that employ electromagnetic currents to spot fatigue and corrosion.

Southwest routinely serves more than 1 million arriving and departing passengers every month at McCarran.

Michael Boyd, president of the consulting firm Boyd Group International in Evergreen, Colo., considers both Southwest and the 737-300s safe to fly.

"The majority of their fleet are 737-700s that are about 7 years old on average," Boyd said late Monday.

Review-Journal writer Tim O'Reiley contributed to this report.