Jonathan Ernst/Reuters
Mnuchin, a former Goldman Sachs banker and film producer, asked for the use of an Air Force jet to travel to Europe for his honeymoon in Scotland, Italy, and France according to ABC News.
The use of the jet was denied, according to the report, but would have cost around $25,000 an hour to operate.
This is the second time that Mnuchin's travel has come under scrutiny. In August, he traveled with his wife, Louise Linton, to Fort Knox in Kentucky for the solar eclipse. The Treasury said that the travel was not improper since Mnuchin was in Kentucky for meetings related to tax reform and the travel of Linton would be reimbursed.
Mnuchin's net worth from his pre-White House investment days is roughly $300 million.
The Fort Know trip launched an internal review of the matter by the Treasury inspector general, according to ABC, and the same office is now looking into Mnuchin's honeymoon request.
The use of such a jet would be highly unusual for a secretary of the Treasury, as military aircraft are typically reserved for cabinet members that deal directly with national security.
A Treasury official told ABC that Mnuchin requested the Air Force jet to ensure he had a secure method of communication and that the request was denied because it was deemed "unnecessary" because their were other ways to securely communicate.