"We can't be out there kicking every tire and watching every wrench being turned," Brown said. "[But] we still do kick a few tires."
Jim Sokol, vice president of maintenance and engineering for Southwest Airlines, which contracts out three-fourths of its jet maintenance to U.S. companies, said Southwest conducts safety audits at least twice a year and sometimes monthly at each of its contractors.
Jeff Green, spokesman for United Airlines, which next month is to begin sending its 52-plane fleet of 777s to China for service, said United maintained staff on site at all its U.S. and foreign repair stations.
"Safety is our No. 1 priority," he said. "It's something we would never compromise."
Industry experts say airlines are motivated to be careful. They can be held legally responsible for maintenance mistakes, outsourced or not, that contribute to accidents.
"My gut reaction," said Ron Kuhlmann, vice president of Unisys R2A, transportation consultants near San Francisco, "is no one is willingly or knowingly going to accept inferior maintenance because the consequences are just too dreadful."
A study by Kuhlmann's company in July found that extensive outsourcing is not a universal practice. But most carriers at least contract out engine maintenance, typically to the manufacturer.
"Most of our work is done with companies that actually designed the equipment," said Southwest spokeswoman Brandy King. "So we feel they know it better than anyone."
Another service that airlines commonly outsource is so-called heavy maintenance: tip-to-tail jet overhauls, performed every few years, that may take two weeks or more.
But Kuhlmann also found another trend: Many U.S. carriers service planes and parts for third parties such as the U.S. military and foreign airlines. The idea is to make money and keep repair stations busy during slow times.
American, which does most of its own maintenance, is courting such business.
Carmine Romano, American's vice president of Tulsa, Okla.-based maintenance, said that in the last five years, his station had cut its turnaround time for engine overhauls by half or more to compete for contracts.
It recently won a bid to maintain 29 aircraft for a Brazilian start-up airline.
You might call this in-sourcing — one of many experiments by a troubled industry trying to cut costs and improve efficiency.
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