WASHINGTON (Reuters) - The U.S. Department of Transportation (USDOT) is opening a review of how the 10 largest U.S. airlines collect, handle and use the personal information of passengers.

The review will look at air carriers' policies and procedures to determine if they are properly safeguarding personal information, unfairly or deceptively monetizing that data, or sharing it with third parties, USDOT said Thursday.

USDOT's Office of Aviation Consumer Protection will conduct privacy reviews of Allegiant, Alaska , American, Delta, Frontier, Hawaiian, JetBlue ( JBLU ), Southwest ( LUV ), Spirit, and United.

USDOT sent letters to the carriers asking about policies on passenger personal information, details of complaints alleging airline employees mishandled personal information, and required employee privacy training. 

"Airline passengers should have confidence that their personal information is not being shared improperly with third parties or mishandled by employees," Transportation Secretary Pete Buttigieg said.

USDOT said if it finds evidence of problematic privacy practices the department could open formal investigations, take enforcement actions, issue industry guidance or adopt new rules.

Airlines for America, an industry group, said air carriers "take customers' personal information security very seriously, which is why they have robust policies, programs and cybersecurity infrastructure to protect consumers' privacy." 

Major U.S. airlines have spent $36.6 billion on IT systems since 2018, including $7.4 billion in 2023, the airline group said.

Buttigieg said the department is working on the review with Senator Ron Wyden, who has long advocated for consumer privacy.

"Because consumers will often never know that their personal data was misused or sold to shady data brokers, effective privacy regulation cannot depend on consumer complaints to identify corporate abuses," Wyden said in a statement. 

Mishandling consumers' private information may be considered an unfair or deceptive practice by airlines and can result in civil penalties, USDOT said.

USDOT said in December it was scrutinizing the frequent flyer programs of major U.S. airlines for potential deceptive or unfair practices, the agency said as regulators step up oversight of the airline industry.