Supreme Court Justice Clarence Thomas’s lavish travel provided by Republican donor Harlan Crow included two more flights aboard the billionaire’s private jet that were not publicly disclosed, according to a letter Monday from Sen. Ron Wyden (D-Ore.) to Crow’s attorney.

Wyden, the chair of the Senate Finance Committee, wrote that he is seeking additional information about travel that Crow provided to the justice and additional records because he is concerned that Crow might have improperly used the gifts to lower his tax bills, a claim Crow denies.

The two flights add to a long list of travel and other perks Thomas has received from Crow, including private school tuition for a relative and the purchase of the home where Thomas’s mother lived in Georgia.

The largesse and other ethics controversies swirling around the court prompted President Biden to propose a biding ethics code and 18-year term limits for the justices last week, a package of overhauls that has little chance of passing Congress at the moment.

“The questions I’ve been asking of Mr. Crow and Justice Thomas about these luxury trips and lavish gifts are not really all that complicated,” Wyden said in a statement to The Washington Post. “How many of these trips happened, and when it comes to Mr. Crow’s taxes, is everything on the level or did he claim a whole lot of personal travel as write-offs?”

U.S. Customs and Border Protection documents show Thomas and his wife, Virginia “Ginni” Thomas, took a roundtrip flight from Hawaii to New Zealand aboard Crow’s private jet in November 2010, according to the letter. Crow was onboard the flights.

It was unclear how the Thomases traveled to Hawaii or how they got home.

Wyden wrote that Thomas has not listed the flights in financial disclosure forms that Supreme Court justices are required to file, even though he has previously amended the forms to include other travel aboard Crow’s jet.

Thomas did not immediately respond to a request for comment. He has said disclosure rules at the time of the travel did not require him to report the flights because they fell under a “personal hospitality” exemption. Justices are now required to report such travel.

Michael Zona, a spokesman for Crow, said in a statement that Wyden’s inquiries are “intended to harass a private citizen” and that Congress has no role in tax enforcement.

“Mr. Crow and his businesses are in good standing with the IRS,” Zona said. “He has always followed applicable tax law as advised by national accounting firms who serve as his tax advisors. It’s concerning that Senator Wyden is abusing his committee’s powers as part of a politically motivated campaign against the Supreme Court.’