The Transportation Department Office of Inspector General (OIG) will review 18 flights Buttigieg made on Federal Aviation Administration-operated (FAA) planes on seven total trips after a request by Republican Senator Marco Rubio.

The costs of the flights for Buttigieg and staff was $41,905.20, and in six of seven trips costs to fly on FAA planes were less expensive than flying commercial, a department spokesperson confirmed to Reuters, adding it "will fully cooperate with the IG on this."

"Glad this will be reviewed independently so misleading narratives can be put to rest," Buttigieg wrote on Twitter. "Bottom line: I mostly fly on commercial flights, in economy class. And when I do use our agency’s aircraft, it’s usually a situation where doing so saves taxpayer money."

The OIG said it will review if the Office of the Secretary complied with regulations, policies, and procedures regarding executive travel on government aircraft and will "focus on official trips taken since January 31, 2017."

Elaine Chao served as Transportation secretary from 2017 through early 2021 under President Donald Trump.

The Washington Post first reported the audit.

Rubio requested the review in December after Fox News reported on the flights and asked if any violations of Transportation Department policy were identified.

"American taxpayers deserve assurances that their tax dollars are not wasted by the government's highest officials," Rubio wrote.

A 1992 White House memo allows senior government officials to travel on government aircraft but with restrictions.