Regulators failed to hold Southwest Airlines to account for not meeting safety standards, putting as many as 17 million passengers at risk on tens of thousands of flights, a federal watchdog said in a report on Tuesday.

The report found that the Federal Aviation Administration had allowed Southwest to routinely provide inaccurate data to pilots and to operate more than 150,000 flights on planes whose airworthiness had not been confirmed.

The agency also failed to investigate concerns raised by its own representatives “ranging from senior executives to local inspectors” over Southwest’s safety culture, according to the report, issued by the inspector general’s office at the Transportation Department.

It cited accusations from F.A.A. officials that Southwest used “diversion, distraction and power” to get what it wanted and would regularly bypass local officials by going straight to F.A.A. headquarters. The investigation was prompted by a hotline complaint and an engine explosion on a Southwest flight in April 2018 that was responsible for the first death on a U.S. airline in nine years.