Interior Secretary Ryan Zinke, in a speech at the Heritage Foundation in Washington, D.C., on Friday, said stories about his travel are "a little B.S."

His comments come after Politico first reported he billed taxpayers for a $12,000 flight on an oil company's charter plane from Las Vegas to a place close to his home in Montana. Zinke dismissed the story, as other secretaries — especially Health and Human Services Secretary Tom Price — are under scrutiny for their tax-funded plane travel. Zinke said he flies coach, only taking a charter when necessary on three occasions.

"I'd just like to address in the words of General Schwarzkopf, a little B.S., on travel," Zinke told his audience Friday. "And I just want to read a little statement for ya so you have it. I said, I believe taxpayers absolutely have the right to know official travel costs. It's common sense and at the department we make those documents and my travel schedule available to everyone. Using tax dollars wisely and ethically is a greatest responsibility and is at the good heart of good government. And there are times, however, we have to utilize charter services because we often travel in areas that are under circumstances that we don't have other flight options. I fly coach. Since being sworn in, I've used a charter on three occasions."

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Zinke explained each of the instances when he took non-commercial flights. The first time as secretary, he said, was when he was invited on a bipartisan congressional delegation by the Senate Energy and Natural Resources Commission to the Arctic Circle. The next flight was a late-night flight to Montana, where he was scheduled to speak to the Western Governors Association the next morning. The final flight involved ravel to and between islands in the U.S. Virgin islands, he said.

"Every time I travel I submit the travel plan to the ethics department that evaluates it line by line to make sure that I am above the law," Zinke said. "And I follow the law. Of course, we are always continuing to look at ways to lower costs in the department and also as you'll find out, to increase revenues. And I'll always be honest and up front about my travel. In fact, you can follow me on Twitter. So if you follow me on Twitter you knew that I traveled by suburban from Valley Forge this morning."

Zinke's travel, on its face, pales in comparison to Price's travel. Price's domestic charter travel exceeds $400,000, according to Politico, which first reported the story, and his international travel on military jets exceeds $500,000, also according to Politico. Price said he will pay back the federal government for the cost of his seat on domestic travel, which he believes is valued at nearly $52,000. But Mr. Trump this week said he was "not happy" with Price, and didn't rule out firing him. That was before Politico's story about the military jet travel broke. Price's travel is under investigation by the HHS inspector general.

Environmental Protection Agency Scott Pruitt spent at least $58,000 on non-commercial travel, CBS News' Julianna Goldman has reported.

Treasury Secretary Steve Mnuchin's travel is also under review by the Treasury Department inspector general, after he reportedly used a government plane to view the eclipse with his new wife.