The U.S. Transportation Department's inspector general is auditing the Federal Aviation Administration's oversight of Southwest Airlines Co after a midair incident in which an engine exploded and one person was killed.

The inspector general's office said in a memo it is opening a new review after "recent events have raised concerns about FAA's safety oversight, particularly for Southwest Airlines."

The inspector general said "our objective is to assess FAA's oversight of Southwest Airlines' systems for managing risk." The office will write a report after it completes the review and may make recommendations.

A Southwest Boeing 737 engine failed in midair on April 17 after it lost a fan blade, killing one passenger. Fragments of the fan blade struck the fuselage, prompting an emergency landing in Philadelphia.

In August 2016, a Southwest flight safely made an emergency landing in Pensacola, Florida, after a fan blade separated from the same type of engine and debris ripped a hole above the left wing.

The inspector general cited the 2016 flight "but it is unclear what actions the carrier took to manage the risk to prevent a future failure."

The FAA, which oversees U.S. civil aviation, said on Thursday it welcomes the inspector general's "examination of the FAA's oversight of Southwest Airlines."

The FAA said its oversight system is designed "to identify potential risks before they become serious problems and ensure that corrective action is taken."

Southwest said it has "a very transparent and professional relationship with" the FAA and welcomes "any additional enhancements or oversights" into its safety management system.

The inspector general said it recently received a complaint "regarding a number of operational issues at Southwest Airlines, such as alleged pilot training deficiencies, which raise concerns about FAA's oversight of the carrier."

In May, the FAA said federal investigators were assigned last year to monitor Southwest maintenance operations, after whistleblower complaints of mistreatment of mechanics raised concerns.

The agency said it found no rule violations and that the assignment of additional inspectors was standard practice to preclude any deterioration in maintenance.

On Monday, the inspector general launched a separate audit of FAA oversight of aircraft evacuation procedures. The FAA requires an aircraft to be fully evacuated in 90 seconds or less.

The inspector general said industry tests for certifying new aircraft have not been significantly updated since 1990, noting airlines have added seats and shrunk the space between seats, which could change evacuation times.