WASHINGTON – Dallas air traffic controllers hid dozens of safety errors that allowed planes to fly too close together, federal officials said Thursday.

Air traffic officials blamed pilots for the errors when controllers were actually to blame, the Federal Aviation Administration said. Though most of the incidents were not serious, a handful were classified as significant safety risks, said Hank Krakowski, the agency’s newly appointed chief of air traffic.

The revelations marked the second time in the past two months that federal whistle-blowers raised safety concerns at the FAA. The FAA admitted in March that inspectors overseeing Southwest Airlines allowed the carrier to fly planes that had not received critical safety inspections. A subsequent review of all airlines’ maintenance triggered massive groundings after additional safety violations were found, disrupting travel for hundreds of thousands of people.

A federal watchdog who shepherded whistle-blower allegations in both cases charged that the FAA suffers from a culture of “complacency and cover-up.”

“This culture did not develop on its own,” said U.S. Special Counsel Scott Bloch. “I believe it happened with the complicity of higher management and could not have been possible without the support of leadership in Washington.”

FAA officials said that the falsification of error reports appears to be limited to Dallas. They announced a series of steps to prevent it from occurring again.

“We’re not going to stand for this,” said acting FAA Administrator Robert Sturgell.

Federal investigators with the Transportation Department’s inspector general corroborated allegations from whistle-blowers that controllers monitoring flights within 40 miles of Dallas routinely and intentionally falsified reports involving planes that flew too close together, the FAA said.

The inspector general’s office found that controllers claimed that 62 such incidents between November 2005 and July 2007 were the fault of pilots when, in fact, controllers had caused the error. Inspector General Calvin Scovel’s report has not been officially released but was described by the FAA.

Similar allegations against the Dallas facility were made in 2004 by a whistle-blower, and the FAA promised to reform how errors are reported. However, the fixes “were not executed appropriately,” and falsification of records continued, Krakowski said.