WASHINGTON (AP) -- The Federal Aviation Administration announced Thursday its second effort in three years to stop its managers in Texas from covering up air safety violations -- after a new investigation found the misconduct continued into last year.

In the latest blow to an agency already under fire for letting airlines ignore its safety directives, the FAA announced that the top two managers of an air traffic control facility in Dallas-Fort Worth had been removed from their jobs.

In addition, the Transportation Department's inspector general found FAA managers in Dallas-Fort Worth routinely and intentionally misclassified instances where airplanes were allowed to fly closer together than they were supposed to, the FAA said. Instead of calling them operational errors or deviations from safety rules by FAA controllers, the managers labeled them pilot errors or nonevents.

"We're not going to stand for this," acting FAA administrator Bobby Sturgell told a news conference.

Hank Krakowski, a former United Airlines pilot and safety executive who became FAA's chief operating officer last September, acknowledged that FAA had promised to fix the problem in 2005 but "today it's clear to us those commitments were not taken seriously by people in my organization who were responsible." He announced a new attempt to remedy the problem.

The FAA only learned of the continuing problem because a whistle-blower - controller supervisor Anne Whiteman, who first reported in 2004 that agency officials were concealing safety violations - had come forward again last year to say the FAA managers were still underreporting safety violations by FAA controllers or now misreporting them as pilot errors.

The new inspector general report that substantiated Whiteman's latest allegations was ordered last year by the U.S. Office of Special Counsel, an independent investigating agency responsible for protecting whistle-blowers. A brief summary of the findings was issued by the FAA. Special Counsel Scott Bloch did not plan to release the report until he had time to evaluate it in detail with whistle-blowers but said it "seems to validate what our brave whistle-blower Anne Whiteman brought forward."

"I continue to be concerned about a national trend," Bloch said in a statement referring to the Dallas-Forth Worth cover-up and the recent disclosure of lax FAA supervision of safety compliance by Southwest Airlines and American Airlines. "These problems exist because of a culture of complacency and cover-up in the FAA. This culture did not develop on its own. I believe it happened with the complicity of higher management and could not have been possible without the support of leadership in Washington."

Transportation's inspector general found that between November 2005 and July 2007, FAA managers at the Dallas-Fort Worth facility misclassified 62 air traffic events as pilot deviations or nonevents when in fact there were 52 operational errors and 10 operational deviations by FAA controllers, the FAA said.

Krakowski said the problem appeared to be confined to the Dallas-Fort Worth TRACON, a facility that controls flight below 10,000 feet and within 30 miles of the Dallas-Fort Worth airport and several smaller airports nearby. He said a nationwide sampling found only 3 percent misclassifications elsewhere but 25 percent there.

The air traffic controllers' union, deep into a two-year-old fight with the FAA over manpower and safety, pounced on the agency's announcement to again criticize what it considers a shortage of workers. The Dallas-Fort Worth facility has 57 fully certified controllers, down from 99 in January 2006, said Darrell Meachum, vice president of the National Air Traffic Controllers Association's southwest region.

Meachum said 45 operational errors were reported in the first six months of this fiscal year, up from 26 over the same period in 2007.

"The system is broken," Meachum said. "These cover-ups by the FAA are just par for the course."

"This once great aviation safety agency has become 'FEMA with Wings,'" said Meacham, referring to the Federal Emergency Management Agency which bungled the response to Hurricane Katrina.

The FAA says it has been able to replace controllers who resign or retire with new hires who can work some but not all stations as they complete on-the-job training that can take up to three years. Controllers in training now comprise 25 percent of the national controller workforce, up from 15 percent a few years ago. Controllers union president Patrick Forrey said there are 22 trainees at the Dallas-Fort Worth facility but nine of them are not yet certified to handle any radar position.

To deal with the problem in Texas, Krakowski announced four nationwide steps because "I'm not confident it can't happen elsewhere:"

The cause of safety violations will no longer be determined by managers of air control facilities, but rather by a national quality assurance team that will also audit facility reports. This team will report to Krakowski's top safety officer.

Krakowski's newly hired safety officer, Air Force Brig. Gen. Robert O. Tarter, will do a complete safety review of all procedures in FAA's Air Traffic Organization.

By the end of this year, FAA will install in Dallas-Fort Worth software that electronically detects any loss of the required distance between airplanes and will install it nationwide by the end of 2009.

A recently signed agreement with the controllers union, similar to one already in place for pilots, will allow air traffic controllers to report safety problems without fear of penalties.

Associated Press Writer Paul Weber in Dallas contributed to this report.

Copyright 2008 The Associated Press.