WASHINGTON (AP) – For more than a decade, Northwest Airlines repeatedly failed to follow federal safety orders but wasn't held accountable by the Federal Aviation Administration, according to a government report.

The report by the Transportation Department's inspector general's office confirmed many of the allegations brought by a whistle-blower in 2005 and again in 2008 of a cozy relationship between FAA managers and the airlines they are charged with inspecting.

FAA inspector Mark Lund charged that FAA managers at the safety office that oversaw Northwest routinely allowed the airline to avoid penalties or fines by voluntarily disclosing failures.

In response, the FAA headquarters initiated a national review of safety order compliance at major airlines in 2008 that found 14 instances in a four-month period in which Northwest didn't comply with safety orders, one of the highest of all the airlines reviewed, the IG report said.

The failure to comply with FAA safety orders continued even after FAA's review, the report said. There were eight more instances in which Northwest didn't carry out safety orders in the budget year ending on Sept. 30 2009, the report said. The FAA office overseeing the airline closed five of those cases without recommending penalties or fines.

In one of those cases, Northwest had to ground 27 planes because it hadn't inspected landing gear parts as required by a safety order. The inspections were intended to prevent the main landing gear from separating from the wing and possibly rupturing a fuel tank, the report said.

Given that the problems have continued, "the status of Northwest's compliance with more than 1,000 (safety orders) is unknown,'' the IG report said.

The IG report is dated December 7, 2009. It was released this week by the US Office of Special Counsel, which handles federal whistle-blower complaints.

Northwest merged with Delta Air Lines last year, creating the world's largest airline. It now flies as Delta.