"We had a safety record in the 1990s that, at today's air-traffic level, would produce a fatal accident every month," said Basil Barimo, vice president of safety and operations for the Air Transport Association, a trade group.
"In 2007, we had zero fatal accidents. In many ways, having a close relationship between the airlines and FAA is absolutely critical."
Yet to others, including influential members of Congress and a union representing FAA inspectors, the system is fragile and depends too much on airlines' following every step of the aircraft-maintenance process to the letter of the law. The union says the FAA's senior administrators seem to be more concerned with keeping airlines solvent rather than safe, an accusation the FAA rejects.
An FAA inspector's job today mostly involves checking computerized records kept by carriers to make sure that required maintenance work was done, rather than actually inspecting planes, said Linda Goodrich, vice president of the Professional Aviation System Specialists union.
The union estimated there are about 2,800 FAA inspectors today, about 30 percent fewer than a decade ago.
"Is it safe?" Goodrich said. "We, and they, don't even know. . . . We won't know until there's a smoking hull."
Questions about the system have arisen from a week of intense scrutiny of Southwest's maintenance practices, first revealed when the FAA announced a record $10.2 million fine to penalize the airline for allowing dozens of planes to continue flying despite missing scheduled maintenance work.
Rep. James Oberstar (D., Minn.), chairman of the House Transportation and Infrastructure Committee, called the case "the most serious lapse in safety I have been aware of at the FAA in the past 23 years," based on evidence from agency employees themselves.
The employees, two inspectors assigned to oversee Southwest maintenance at the company's Dallas headquarters, used federal whistle-blowers' protection to complain that the lapses had occurred, in part, because managers at the airline and their bosses at the FAA had become too friendly with one another.
After first vowing to fight the FAA penalty, Southwest suspended three maintenance managers this week and took extra steps to comply with regulations requiring it to inspect older Boeing 737 jets for cracks caused by metal fatigue.
On Wednesday, Southwest grounded 44 planes for a day to reexamine areas of their fuselages for cracks. All the planes already had been checked, using either a visual inspection or equipment that finds tiny fissures not visible to the naked eye, but Southwest decided to use both methods on each aircraft, spokeswoman Whitney Eichinger said. The airline, which has 62 daily departures from Philadelphia, said its schedule was back to normal yesterday.
Careful inspections are vital because of what has been learned about metal fatigue since an Aloha Airlines accident 20 years ago in which part of the roof of a 737 was ripped off in flight, killing a flight attendant. Airlines since then have been required to obsessively check older planes for tiny cracks.
But experts generally agree that it is physically impossible for FAA inspectors to also make the same metal-fatigue checks and personally watch to see that airlines are doing a myriad of other inspections the law requires.
A decade ago, the FAA began moving from a system of inspectors that randomly drop in at airline-maintenance bases to make spot checks to one that requires more meticulous record-keeping by the carriers to show that required work was done. FAA inspectors spend most of their time now checking those records, the union's Goodrich and others said.
Criticizing the FAA's approach, Goodrich said its management "finds no value in us just stopping by and taking a peek, asking why is that plane back in here for a third time for maintenance."
But others say the industry's safety record and self-interest in maintaining airplane fleets to secure travelers' loyalty show the cooperative approach is working.
"If you're not safe, accidents happen and no one will fly you," said Fred Mirgle, chairman of the aviation-maintenance science department at Embry-Riddle Aeronautical University in Daytona Beach, Fla.
The safety network is based on FAA inspectors that develop good relationships with airline officials and anyone else who operates airplanes - including his own school, the owner of 70 planes used for training - so the agency trusts them to do what is required, Mirgle said.
"I don't think coziness had anything to do with it," he said. "Those relationships are important, not so much to be cozy but to be truthful and honest."
In the case of Southwest's maintenance, Boeing Co., which builds the 737, and a former chief investigator for the National Transportation Safety Board hired by the airline said the inspections that had not been completed on time were not "safety-of-flight" issues. That means that in their opinion, shared by many in the aviation business, the maintenance lapses did not endanger an airplane, its passengers or crew.
"My understanding is that it was not a flight-safety issue, but it was absolutely a compliance issue," said Richard S. Golaszewski, executive vice president of GRA Inc., a Jenkintown consulting firm that has done work for airlines, airports and the FAA.
"It was not an issue of was an airplane going to fall out of the sky, but was someone not complying."
Contact staff writer Tom Belden at 215-854-2454 or email@example.com.