WASHINGTON, May 9 (Reuters) - The U.S. Transportation

Department Office of Inspector General (DOT OIG) will audit the

Federal Aviation Administration's oversight of United Airlines

maintenance practices, the agency watchdog said on Thursday.

"We will evaluate FAA's actions to address maintenance

non-compliances and violations at the air carrier," the DOT OIG

said on its website.

Over the past five years, the inspector general has issued

several audit reports and recommendations on FAA's oversight of

maintenance at Allegiant Air, Southwest Airlines ( LUV ), and

American Airlines ( AAL ) and is currently reviewing SkyWest

Airlines.

United and FAA did not immediately comment.

In March, the FAA said it was increasing its oversight of

United following recent safety incidents, saying it would

initiate a formal evaluation to ensure the Chicago-based airline

was complying with safety regulations.

The DOT OIG said on Thursday: "recent safety events with

United Airlines -- such as flight diversions that can be traced

to mechanical problems -- serve to remind us that FAA oversight

of maintenance programs is paramount."

The FAA said in March it may delay future United

certification projects "based on findings from oversight."

A 2020 DOT OIG report said Southwest ( LUV ) operated more than

150,000 flights carrying 17.2 million passengers on the jets

without confirming it had completed required maintenance.

In 2020, the FAA sought to impose a $3.92 million fine on

Southwest ( LUV ) for alleged weight infractions on 21,505 flights in

2018 on 44 aircraft, and in 2021 the investigation was resolved

with a $200,000 civil penalty and deferring the remaining civil

penalty based upon corrective actions accomplished by Southwest ( LUV ).

A 2021 DOT OIG report said the FAA lacked effective

oversight controls to ensure American Airlines ( AAL ) corrective

actions for maintenance issues address root causes.

The report found that in one instance American "flew an

aircraft with an inoperable emergency evacuation slide for 877

days before reporting the non-compliance to FAA."