Under fire for expensive private flights, Health and Human Services Secretary Tom Price said Thursday he would stop taking charter planes for official business and that he would pay back the US Treasury at least some of the costs for the flights he had already taken.

It was Price’s most public contrition yet, as Democrats have called for him to resign and President Trump has left the secretary’s future with the administration in doubt.

“I regret the concerns this has raised regarding the use of taxpayer dollars. All of my political career I’ve fought for the taxpayers,” Price said in a statement. “It is clear to me that in this case, I was not sensitive enough to my concern for the taxpayer. I know as well as anyone that the American people want to know that their hard-earned dollars are being spent wisely by government officials.”

Price said he would continue to cooperate with an ongoing internal investigation of the flights, which were brought to light in a series of reports from Politico.

“The taxpayers won’t pay a dime for my seat on those planes,” Price said. He appears to have meant that literally — the total cost of the flights had been more than $400,000, according to Politico, and Fox News reported Thursday that Price would pay a little less than $52,000.

The practice was a sharp departure from his predecessors under the Obama administration, Politico noted, who usually flew commercial. Ethics experts have questioned the propriety of such trips.

“This wasteful conduct reflects disdain for the ethical principle of treating public service as a public trust,” Walter Shaub, who ran the US government ethics office under President Barack Obama, told Politico. “Public office isn’t supposed to come with frivolous perks at taxpayer expense.”

Price’s office had previously sought to defend the secretary, arguing he flew by charter when commercial flights were unfeasible and painting the travel as part of his efforts to reach ordinary Americans, including those ravaged by the hurricanes of the past few weeks.

But according to the Politico reports, Price had still flown privately even when there were viable commercial alternatives, and the charter flights started well before these recent natural disasters.

Tom Price’s charter flights, explained

The scandal started last week, when Politico reported that Price had taken five private flights over the past week, costing taxpayers tens of thousands of dollars. The outlet cited internal HHS documents.

He traveled to Maine, New Hampshire, and Pennsylvania, all for health care–related events.

In a general response to the report at the time, an HHS spokesperson said, “When commercial aircraft cannot reasonably accommodate travel requirements, charter aircraft can be used for official travel.”

Politico readily disputed that explanation.

An example: Price took a charter flight from Washington Dulles International Airport to Philadelphia, departing at 8:27 am. A commercial United Airlines flight left at almost the exact same time. The United flight would have cost less than $750; the charter trip cost $25,000, according to Politico.

Politico reporters Dan Diamond and Rachana Pradhan also noted that Price could have taken an Amtrak train to Philadelphia for less than $100 or been driven by SUV and potentially paid $30 in gas.

Both HHS secretaries under Obama, Kathleen Sebelius and Sylvia Mathews Burwell, flew commercial while traveling in the continental United States, Politico noted. And the Trump administration’s defense — that Price only flew privately when a commercial flight was infeasible — was undercut by further reporting.

Politico eventually reported that Price’s private jet travel was even more extensive: The HHS secretary had taken at least 24 charter flights over the past year. The bill has grown to more than $300,000, the outlet reported, citing federal contracts and people familiar with the situation.

One charter flight from Washington to Nashville cost nearly $18,000, even though there were multiple nonstop commercial flights available that cost as little as $200.

HHS doubled down, arguing that Price was traveling to reach “the real American people,” as the department put it to the Washington Post, and the agency told Politico that Price went to see those devastated by Hurricanes Harvey and Irma.

Then again, Politico noted that 17 of the flights it found occurred before the hurricanes made landfall in the United States. Price also took charter flights to events like the notoriously elite Aspen Ideas Festival and arrived nearly a full 24 hours before his scheduled appearance.

The news outlet later found that Price had used the private flights to visit an island where he owned property and to stop in Nashville to have lunch with his son, further undercutting the HHS defense that the secretary was always on government business.

This isn’t the first time Price’s ethics have been questioned

The private flights have become a sizable scandal on their own, but this isn’t the first time Price’s ethical compliance has been in doubt.

After he was nominated to lead HHS at the beginning of the year, Price endured numerous reports about his personal investments in health care stocks while serving as a Congress member for Georgia’s Sixth District.

As Vox previously explained, Price bought and sold stock in more than 40 health care companies, stocks worth more than $300,000, as a Congress member. Despite appearances, most of those sales and purchases seemed to comply with House ethics rules.

However, there were a number of specific transactions and accompanying actions by Price that raised eyebrows:

In March 2016, according to CNN, Price bought up to $15,000 worth of stock in Zimmer Biomet, a medical device company that specializes in hip and knee implants. Two days later, he introduced legislation to delay a regulation that would have hurt the company’s business by changing how Medicare and Medicaid reimburse those procedures. Zimmer Biomet then donated to his campaign. (Price says he was not aware of the purchase, which was made by his broker.)

Price also bought shares in six pharmaceutical companies a week after a federal regulation was proposed that would lower reimbursements for doctors who prescribe expensive drugs for cancer and arthritis, according to Time magazine. The regulation was meant to help control health care costs by encouraging doctors to prescribe generic drugs and cheaper alternatives instead, and would have hurt pharmaceutical companies’ bottom lines. The companies lobbied against the regulation, and Price sponsored legislation to block it. It was never enacted.

Price was able to take advantage of a special deal in another biotech firm, Innate Immunotherapeutics, an Australian company developing a multiple sclerosis drug, according to Kaiser Health News. Price was offered discounted shares for “sophisticated investors” in summer 2016 after making a smaller investment in the company in 2015. (A fellow member of Congress, Rep. Chris Collins, is on the company’s board; members of the Collins family own about 20 percent of the company.)

Though there was no definitive evidence that Price broke the law, Democrats sought to stop his confirmation amid the controversy. Price was confirmed 52 to 47 — with all Republican votes — in February.