Washington — The Federal Aviation Administration has become so friendly with airlines that it no longer acts as the public's watchdog, whistle-blowers told Congress on Thursday.

"We are told that the airlines are our customers," FAA inspector Charlambe "Bobby" Boutris said. "But we have a more important customer, the taxpayers" who want government to ensure a safe aviation system.

Boutris, who testified before the House Transportation Committee, complained last year about safety issues at Southwest Airlines. But his warnings went unheeded as the airline continued to fly planes not properly checked for cracks in the fuselage.

His chain of command was "downplaying serious safety issues" to please the airline, he said.

Nicholas Sabatini, the FAA's associate administrator for safety, said he himself found it "astounding" that the safety system had failed so badly at Southwest. He promised to make the changes, including the end of the term "customer" to describe airlines.

"We're going to recalibrate that," he said.

Moreover, "we must accept responsibility for mistakes," he said.

Committee Chairman James Oberstar (D-Minn.) advised Sabatini not to focus on disciplining individuals because "the system itself has cracks."

Boutris, who was assigned to the FAA office in Irving, Texas, near Southwest's headquarters in Dallas, had raised warnings about Southwest skipping inspections since 2003. His supervisor, who has since been reassigned, suppressed the information rather than inconvenience Southwest, he said.

Boutris said the problems at Southwest received attention only after he contacted the Office of Special Counsel, a federal office that protects whistle-blowers.

Douglas Parker, another FAA inspector at Southwest, said he, too, "discovered that several aircraft had been operated in an unsafe condition."

Parker's voice faltered as he recounted how last June, while typing up a report about "unethical actions" at Southwest, he got a visit from a supervisor. The manager began picking up photos of Parker's family and commenting on the importance of family obligations.

"On his way out of the door, he made the following statement: 'You have a good job here and your wife has a good job over at the Dallas [FAA office]. I'd hate to see you jeopardize your and her careers trying to take down a couple of losers,'" he said.

Peters said that despite the intimidation, "the poor condition of the Southwest Airlines regulatory oversight was a risk that neither Inspector Boutris nor I was willing to accept."

Oberstar praised the inspectors for trying to uphold "a culture of safety." As long as FAA higher-ups are telling inspectors to treat airline executives as "customers" who must be served, then "that culture of safety is not going to take hold," Oberstar said.

After the incident with the family photos, Peters told an FAA special agent of his experience involving Southwest. The inspectors' concerns centered on the potential for the kinds of fuselage cracks that caused an Aloha Airlines 737 to tear apart in flight a decade ago. The rip allowed a flight attendant to be sucked out of the plane to her death.

After an investigation, the FAA proposed a record $10.2 million fine against Southwest in March for the airline's failure to perform mandatory inspections. The airline placed three employees on leave and grounded 38 planes for new inspections.

The FAA then called for an industrywide review of inspection practices. Beginning in late March, American Airlines, Delta Air Lines and United Airlines each canceled flights to take a closer look at some of their aircraft.

Scott Bloch, from the U.S. Office of Special Counsel, said the FAA has failed to keep pace with growing safety demands as "a culture of convenience and of complacence has evolved."

Calvin Scovel, the inspector general at the Transportation Department, piled on, saying that "we found that FAA's Southwest inspection office developed an overly collaborative relationship with the air carrier." So instead of acting as a watchdog, the FAA allowed Southwest to "self-disclose" any safety violations without having to pay fines or develop "a comprehensive solution for reported safety problems."

Southwest Chairman Herbert Kelleher defended his airline's safety practices, noting that Southwest has never killed any of its passengers.

"We have constantly jawboned our people — that safety is job No. 1," he said.

The airline did not ground the planes with possible problems because airline employees may have "made some engineering judgments they weren't entitled to make," Kelleher said. "We have learned our lesson. I apologize to this committee."

Southwest CEO Gary Kelly agreed that "better judgment should have been exercised" when the decision was made to keep flying uninspected planes. "We will make all of the necessary changes" to ensure safety will never be compromised again, he said.