WASHINGTON (WASHINGTON POST) - The Trump administration, one of the wealthiest in modern US history, is facing widening criticism over travel expenditures among some of the billionaires, budget hawks and business executives who head federal agencies.

Inspectors general have opened at least five investigations into charter or military flights by Cabinet officials amounting to millions in federal spending. Their decisions to veer away from cheaper commercial flights have led to criticism from Democrats in Congress and government accountability groups about a culture of entitlement in Trump's administration.

New examples of questioned expenditures include Energy Secretary Rick Perry, who on Friday (Oct 6) turned over his travel records under pressure from House Oversight Committee Chairman Trey Gowdy, and the panel's top Democrat Elijah Cummings. Environmental Protection Agency (EPA) Administrator Scott Pruitt faces an expanding investigation into his travel by private jet.

The drumbeat of controversy over Cabinet travel threatens to undermine a core pillar of Trump's relationship with his base - his promise to "drain the swamp" of elite Washington, D.C., rein in waste and represent the working class.

Veterans Affairs head David Shulkin last week backed out of a congressional trip to Europe, The Washington Post learnt, after criticism about another international outing, which combined official travel with sightseeing and a Wimbledon tennis event. And Interior Department chief Ryan Zinke faced new criticism about his travel - often accompanied by his wife, who is managing a Republican campaign in Montana - which included stops at political fundraisers and donor events.

Adding to the costs are travel accommodations for Cabinet aides, invited guests and security details, who accompany secretaries on all trips. Thus far, officials have assumed no financial responsibility for passengers on their flights.

Tom Price, a wealthy Georgia physician who resigned at the end of last month as secretary of health and human services (HHS), ran up charter costs of more than US$500,000 (S$682,000) but pledged aUS $51,887 check to reimburse the government for his seats.

An HHS spokesperson told The Post that Price "was under no obligation" to pay but that this was "him wanting to make a gesture."

Trump senior adviser Kellyanne Conway, who travelled with Price several times, is unlikely to repay the government for her travel cost, the White House said, because she was a guest.

To deal with fallout, the White House has imposed a new approval process for charter jet travel by non-national-security Cabinet members. The protocol will be supervised by Chief of Staff John Kelly.

White House approval for military flights, which have long required special permission, came under question when Treasury Secretary Steven Mnuchin ran up at least US$800,000 on such trips, including a flight with his wife to visit the nation's gold stash at Fort Knox. A report last week by the Treasury watchdog said the flights were legal based on Mnuchin's schedule and need for secure communications, but poorly justified.

White House spokesman Raj Shah on Friday called the use of military planes for Cabinet and other essential travelers "sometimes an appropriate and necessary use of resources." One indicator of how the administration has tried to curb expenditures, he said, is the sharp reduction of what are known as military air White House support missions - travel the president must request.

The White House said Trump officials took 77 military flights through Sept. 19, compared with 94 flights taken during the first eight months of President Barack Obama's administration.

Some government accountability groups argue that the Cabinet behaviour reflects the president's own disconnect with government frugality, evidenced by his weekend trips to his private golf clubs and Mar-a-Lago, as well as the costly travels by Trump family members that must be monitored by government employees and Secret Service agents.

"The tone is set at the top," said Noah Bookbinder, executive director of Citizens for Responsibility and Ethics in Washington, a watchdog group that recently called for an investigation into Trump appointees' travel.

"When you have a president who is visiting his private resorts every weekend at great cost to taxpayers, it is not surprising that Cabinet members are using private jets to get to standard meetings."

White House press secretary Sarah Huckabee Sanders has defended Trump's trips as decision-making tools."Every weekend that he's travelling, no matter where he is, the president is working," Sanders said Thursday. "This is a president that is committed to helping move his agenda forward. And certainly I think that those weekends have been very successful in doing that."

Cabinet leaders have historically been background players, pushing their boss' agenda. Trump's appointees have joined in his vow to control spending by imposing employee travel restrictions, cutting programs and leaving positions open.

But in their own travel, many have swapped the cramped cabins of commercial airplanes for private jets, or have travelled across Denmark, France, Italy and the Caribbean while mixing official duties with vacations and political events.

Air travel costs for Mnuchin, a millionaire former Goldman Sachs partner and Hollywood financier, included eight approved military flights this year to destinations such as Italy, West Virginia and Kentucky, according to documents released Thursday by Treasury's inspector general.

Perry has taken six trips on government or private planes, mostly to visit national labs in Washington state, Idaho and New Mexico; nuclear sites in Ohio and Kansas City; and a Pennsylvania coal plant. While the estimated US$56,000 in trips all received ethics approval, many of the destinations are served by less-expensive commercial airlines. It is unclear whether Perry's schedule could accommodate commercial travel.

Zinke, a former Montana congressman and Navy SEAL commander, flew for official business but spoke in Las Vegas to a campaign donor's hockey team, spent a few weekends near his homes out West and attended political fundraisers from Montana to the Virgin Islands. His wife, Lola, often accompanied him on the trips.

An Interior spokesman said the department "has always and will always work to ensure all officials follow appropriate rules and regulations when traveling."

Reps. Peter DeFazio and Grace Napolitano wrote last week to the EPA's inspector general that the Cabinet trips are "symptomatic of a troubling culture that appears to have swept through this administration."

Trump and the Cabinet travel have highlighted tensions among agencies and the White House over contradictory federal spending messages from Republican leaders.

Mnuchin was one of the first to come under fire, scrutinised for a US$26,900 flight to Kentucky aboard an Air Force Gulfstream jet for a trip that coincided with a Fort Knox viewing of the Aug. 21 solar eclipse.

He was not the only one watching the sky: Agriculture Secretary Sonny Perdue that same day attended a "listening session" with farmers in Charleston, South Carolina, a city within the eclipse's path of totality, and then watched the celestial event from the Francis Marion National Forest. He tweeted eight times and thanked Forest Service officials. A Perdue spokesman did not respond to requests for details.

Mnuchin's chief of staff, Eli Miller, earlier this year flew to Palm Beach aboard the private jet of Nelson Peltz, a hedge-fund billionaire who supports Trump's proposal to slash tax rates for the rich. The Treasury Department said ethics officials approved Miller's acceptance of "a seat on a plane from a friend."

Some members of Trump's Cabinet have shown more restraint. Commerce Secretary Wilbur Ross, a 79-year-old billionaire, has flown commercial coach on several international flights, including for trade missions across Asia, Commerce officials said. He has also flown several times domestically through a private jet-share fleet, paying for the flights himself, his spokesman said.

Zinke's travel is sometimes a family affair. Lola Zinke, who has become a frequent presence at the Interior Department, has travelled on several trips official and political, according to participants. The Zinkes also joined a congressional trip to the Arctic. Lola Zinke posted photographs on social media of some of their travels, but the photos were later removed.

An Interior official, who spoke on condition of anonymity, said Lola Zinke "has never taken a flight at the expense of the department" and pays for her meals and transportation in the instances "she occasionally meets her husband while he is traveling." The department declined to provide receipts or other details about the travel.

Questions about the secretary's mixing of official travel and political appearances became more pointed after Lola Zinke signed on in September as campaign manager for Troy Downing, a Republican candidate for a Montana U.S. Senate seat.

Transportation Secretary Elaine Chao prefers to fly commercial, according to her spokesman. But she took small Federal Aviation Administration jets seven times, including to New York and Paris, when her office said it was cost-justified or fit her schedule better.

Mary Peters, who served as transportation secretary under President George W. Bush from 2006 to 2009, said using the FAA fleet may prevent public servants from connecting with regular people

."We needed to experience the same thing American people were experiencing on commercial flights," she said. "We felt we needed to be on the planes with them and travel the way most Americans travel."