With its “Drain the Swamp” battle cry, the Trump administration has pledged to cut government waste and lessen the burden on taxpayers. But American citizens have been footing the bill for members of President Trump’s cabinet to crisscross the world on government planes.

So far, the fallout has been fierce: At least five cabinet secretaries are under review by inspectors general for their taxpayer-funded travels, and the House Oversight Committee is reviewing all travel by senior administration officials.

The travel of Treasury Secretary Steven Mnuchin came under the scrutiny of the inspector general in August. While previous Treasury secretaries have been known to use military planes for overseas trips, they have generally flown commercial for domestic travel because of the exorbitant costs of operating government jets.

As a practice, Timothy F. Geithner, President Obama’s first Treasury secretary, flew commercially, always in coach, when traveling domestically, Jenni LeCompte, who served as Mr. Geithner’s assistant secretary for public affairs, said on Wednesday.

Mr. Mnuchin, a former Goldman Sachs banker and a onetime Hollywood film financier, appears to break tradition. For example, it cost taxpayers $172,283 for Mr. Mnuchin to fly to Florida, Kentucky, Las Vegas, Washington, D.C., and West Virginia on a military plane. It could have cost $3,402 — about 50 times less — if he had flown commercial.

Cost of Domestic Trips on Military Planes vs. Flying Coach Steven Mnuchin’s Trips Cost of Flights Highest Price

to Fly Coach Miami 43,726 706 A conference and a meeting with the Mexican finance minister. New York to Washington, D.C. 7,556 754 One-way flight after meeting with President Trump at Trump Tower. Louisville and Fort Knox, Ky. 26,900 703 Luncheon and visit to gold reserves. Parkersburg, W. Va., and Las Vegas 94,101 1,239 Meetings with members of Congress and local business leaders. Total 172,283 3,402 The price shown is the highest for booking a coach seat on expedia.com for a next-day trip in late October. Round-trip flights originated in Washington, D.C., except where noted.

Mr. Mnuchin has flown on commercial flights and has used Amtrak “a couple of times over the past several months,” according to a Treasury spokeswoman.

But this month, the Treasury Department’s Office of Inspector General reported that since March Mr. Mnuchin had used military aircraft for seven trips — four domestic and three overseas — for a total cost of more than $800,000. Flying commercial on all seven trips would cost at most about $22,700.

Cost of International Trips on Military Planes vs. Flying Coach Steven Mnuchin’s Trips Cost of Flights Highest Price

to Fly Coach London, Berlin and Baden-Baden, Germany 301,167 4,698 Meetings with Group of 20 finance ministers. Bari, Italy 314,442 11,989 Meetings with Group of Seven finance ministers. Ottawa 16,350 2,578 Meetings with Canadian finance minister and business leaders. Total 631,959 19,265 The price shown is the highest for booking a coach seat on expedia.com for a next-day trip in late October. All flights were round trips from Washington, D.C.

There are a few reasons that government officials take military flights. In Mr. Mnuchin’s case, he has said that his requests for government aircraft were made in the interest of national security — military aircraft are equipped to handle secure communications for officials in flight.

Other Trump administration officials, like Scott Pruitt, the administrator of the Environmental Protection Agency, have taken military or chartered flights because they had scheduling conflicts or commercial flights were not available to their destinations.

Tom Price, the former health secretary, resigned after racking up at least $400,000 in chartered flight fees.

It is usually the White House’s duty to approve a military flight when a cabinet member requests one, in large part because the trips are so expensive. But the inquiry into Mr. Mnuchin’s flights by the inspector general revealed that both White House and Treasury officials failed to meet the normally rigorous standards to get the costly flights approved.

“What is of concern is a disconnect between the standard of proof called for” by White House guidance “and the actual amount of proof provided by Treasury and accepted by the White House in justifying these trip requests,” according to a memo submitted this month by Richard Delmar, counsel to the inspector general.

It cost more than $26,000 to operate the plane for the round-trip flight Mr. Mnuchin took in August to visit Louisville and Fort Knox in Kentucky. The trip attracted attention after Mr. Mnuchin’s wife, Louise Linton, posted on Instagram a photo of herself disembarking a military jet.

The photograph that Louise Linton posted on Instagram.

After visiting the gold reserves in Fort Knox, Mr. Mnuchin and Ms. Linton viewed the solar eclipse. Mr. Mnuchin reimbursed the government $595.90 for the cost of his wife’s travel, according to Mr. Delmar.

Here’s how the Defense Department broke down the cost of the flights:

Expense Cost Aircraft maintenance 8,174 Fuel 1,214 Consumables and repair parts 371 Crew 316 Hourly operating cost of C-37B jet 10,075 x 2.67 hours Total cost of flights 26,900