Transportation Secretary Elaine Chao had planned to fly commercial to Detroit in early June for events on the future of American roads. Then, days before, the White House derailed her plans, organizing an "infrastructure week" speech in Washington alongside President Trump.

But Chao had a special perk to keep her schedule on track: a small fleet of taxpayer-funded executive aircraft that have long served the U.S. and international travel needs of transportation secretaries. Chao attended both cities' events with the help of a Cessna business jet that the Federal Aviation Administration charges other government agencies nearly $5,000 an hour to fly.

Because of the FAA fleet, Chao — who is married to Senate Majority Leader Mitch McConnell (R-Ky.) — was back in Washington in time for a Capitol Hill discussion two days later on commercial airline fees.

Chao has flown on the government's Gulfstream IV and two leased Cessnas seven times in the past eight months, including during day trips to cities about an hour's flight from Washington, as well as longer official sojourns to France and Italy for which flights cost taxpayers tens of thousands of dollars.

Chao's use of the FAA planes is a new twist in the controversy over highflying Cabinet members running up extravagant costs at taxpayers' expense. Agencies that have government aircraft at their command must justify using them with either comparative pricing analyses or explanations of why they needed to incur extra costs because of scheduling difficulties or security concerns.

In previous administrations, some officials said, the restrictions made them pause before bringing out the high-priced FAA fleet.

"Rarely ever did we use anything but commercial," said Mary Peters, who was transportation secretary from 2006 to 2009 under President George W. Bush. The agency, she said, did a cost-benefit analysis for every domestic flight and almost always found it was more cost-efficient to fly commercial. Peters said she flew only "a handful of times" domestically on the FAA planes.

Marianne McInerney, Chao's spokeswoman, said that the secretary also exercises caution and typically flies coach class on commercial flights. Chao took 38 commercial flights this year.

The Transportation Department's ethics counsel has approved all of Chao's government flights, which underwent a similar cost analysis, McInerney said. Past secretaries, she added, have used the government planes far more often: Anthony Foxx, Chao's predecessor and a nominee of President Barack Obama, flew on government jets on 116 trips from 2013 to 2017. Foxx did not immediately comment.

Chao uses government aircraft, McInerney said, only when flight costs for her staff and protective detail are cheaper than flying commercial, or to meet specific security or scheduling demands.

"The secretary is very sensitive to concerns about appropriate use of taxpayers' funds," McInerney said.

The FAA's three jets, stored at Ronald Reagan Washington National Airport, are regularly loaned out to other federal agencies. The planes have been used to transport federal prisoners, shuttle investigators to accident sites, and deliver officers and K-9 units to hurricane sites.

The department did not provide estimates for Chao's flight costs and said it does not reimburse for the flights because it is the FAA's parent agency. When the planes are loaned out to other agencies, the FAA charges $5,644 an hour for the Gulfstream and $4,922 an hour for the Cessnas, factoring in the costs for pilots, maintenance, fuel and leasing.

Taxpayer costs for flying government planes can climb quickly compared to commercial airlines. The median nonstop flight from Washington to Detroit last year cost $208 in coach and $660 in first class, according to the airline data site FlightAware.

New information about Chao's use of FAA planes comes amid revelations about other Cabinet members who spent tens of thousands of taxpayer dollars for government, military or charter planes — eschewing commercial air seats that were a fraction of the cost.

Health and Human Services Secretary Tom Price resigned last week amid criticism about billing the government for more than $500,000 in charter flights. His staff said he chose charters in part so he could avoid the inconvenience and expected delays of commercial airline travel.

Chao's government aircraft use is not unusual. Former transportation secretaries regularly used government planes. Officials from the Obama, Bush and Clinton administrations said previous Transportation Department leaders limited their private flights, adhering to a cost formula to determine whether flying with their official entourage in an FAA jet justified the expense.

An official in the George W. Bush administration who worked for transportation secretaries Peters and Norman Y. Mineta recalled that FAA planes were used only for domestic flights when the secretary needed to make several appearances in a day and commercial flights were not feasible.

In June, less than two weeks after her Detroit flight, Chao and her team flew on the Gulfstream to the Paris Air Show, an international event for military and commercial aircraft long attended by U.S. transportation leaders.

Three days later, Chao flew to the Italian island of Sardinia, where she spoke to a Group of 7 summit ministerial conference. Chao's European trip, McInerney said, was packed with official meetings and included "no personal time." The return flight from Italy was 11 hours, which, at the FAA's discounted internal flight-hour rate, would have cost taxpayers nearly $37,000.

Many past transportation secretaries, including Foxx and his predecessor Ray LaHood, flew FAA planes to European events because of security concerns. The transportation secretary traditionally travels with at least two armed guards, who face additional hurdles when flying commercially.

Most of Chao's FAA flights have been domestic, including in August, when she flew in the government Cessna from the nation's capital to South Bend, Ind., for a ribbon-cutting event for a toll road and a closed-door meeting at the local airport.

The plane was used, McInerney said, "because it was a more cost-effective and efficient way to get the secretary and her staff to South Bend and back to Washington in the time required."

Chao also took FAA planes to Beaumont, Tex., in March; to Columbus, Ohio, in April; and to New York in June, three days after her trip to Detroit. For the New York trip, McInerney said, Chao's office considered commercial and rail travel but decided on the government planes because her schedule was too busy.

Chao traveled to New York again on Aug. 15 to attend a news conference with President Trump. To get there, she took a military C-37 jet that costs about $25,000 an hour to fly, Air Force records show.

Treasury Secretary Steven Mnuchin rode the plane back to Washington that afternoon. The Treasury inspector general is reviewing Mnuchin's flights.

Chao's office said she had intended to fly commercially that day but was invited to go on the military jet. The Transportation Department did not request the jet or pay for it, her office said.

Chao, a labor secretary in the George W. Bush administration, was confirmed as transportation secretary in late January. Her husband, McConnell, has never joined her on official travel, McInerney said.

The Gulfstream, a business jet that fits about a dozen passengers, was bought in 1989, while the two Cessna Citation Excels, which are about 14 years old, are leased. Passengers have described them as relatively austere.

"There is no flight attendant," McInerney said. "No food or drinks are provided."

Jack Gillum, Ashley Halsey III, Lisa Rein and Julie Tate contributed to this report.