The Director of the Office of Management and Budget, Mick Mulvaney, has released a memorandum directed at the heads of executive departments and agencies in the federal government, calling on them to use commercial air transport where possible.

Mulvaney’s memorandum comes in the wake of the resignation of Health & Human Services Sec. Tom Price after it emerged that he had spent roughly $1 million on private planes. Similar allegations of misuse of travel expenses have also been made against other members of the Trump Cabinet, including Treasury Sec. Steven Mnuchin and Interior Sec. Ryan Zinke.

“Government-owned, rented, leased, or chartered aircraft should not be used for travel by Government employees, except with specific justification,” Mulvaney stated.

“Departments and agencies should recognize that we are public servants. Every penny we spend comes from the taxpayer,” he added. “We thus owe it to the taxpayer to work as hard managing that money wisely as the taxpayer must do to earn it in the first place.”

“Just because something is legal doesn’t make it right,” he continued. “Even when the criteria … allow for the use of Government-owned, rented, leased, or chartered aircraft, departments and agencies should still consider whether commercial air travel is a more appropriate use of taxpayer resources.”

“Accordingly, with few exceptions, the commercial air system used by millions of Americans every day is appropriate, even for very senior officials,” he concluded.

Mulvaney also announced a policy shift within the administration in order to tackle this mounting problem, declaring that all future travel on private planes “shall require prior approval from the White House Chief of Staff.”

Director Mulvaney, an ideological libertarian, is seen as a voice of fiscal responsibility in the administration, seeking to cut spending wherever possible. His push on this issue may not be popular with many of his Cabinet colleagues, but will certainly endear him to the American people.