Following reports that the Air Force may be propping up Donald Trump’s failing Scottish golf resort, the Pentagon is conducting a review of flight crews’ trips to Turnberry. The review comes after Politico reported that the House Oversight Committee has for months been investigating the uptick in military expenditures at floundering Prestwick Airport—described as “integral” to accessing the president’s property, as well as the Turnberry club itself, where visiting crews are said to have been offered free rounds of golf. It’s the latest claim that Trump is enriching himself at taxpayers’ expense, and comes as Vice President Mike Pence faces scrutiny for going out of his way to stay at another of the president’s resorts during a recent trip to Ireland. “We are reviewing all associated guidance,” the Air Force said in a statement to Politico on Sunday.

The statement noted that the stopovers did not appear to be “unusual” and that aircrews “adhered to all guidance and procedures,” but added that the service is nevertheless reviewing the matter as Democrats and watchdogs raise ethical concerns. “Given the President’s continued financial stake in his Scotland golf courses, these reports raise questions about the President’s potential receipt of U.S. or foreign governments’ emoluments in violation of the U.S. Constitution and raise other serious conflict of interest concerns,” Rep. Elijah Cummings wrote in a letter to then-Acting Defense Secretary Patrick Shanahan in June.

For the president and those in his immediate orbit, spending big at Trump properties is more or less standard. But questions have become stickier with taxpayer money involved. According to Politico, the military has dropped $11 million since 2017 to refuel at debt-ridden Prestwick, the nearest airport to Trump’s golf club, despite the fact that refueling costs would be cheaper at a military base. The stops—including two earlier this year en route to and from Kuwait—corresponded with improved fortunes for the struggling Trump property: While Turnberry lost $4.5 million in 2017, revenue went up $3 million last year. Democrats have sought documents related to the stopovers as part of its probe, but say they have so far been stonewalled. “The Defense Department has not produced a single document in this investigation,” a senior Democratic aide told Politico.

In a pair of tweets Monday, Trump denied involvement in Pence’s stay at Doonbeg and the Air Force stops in Scotland. “NOTHING TO DO WITH ME,” he wrote of the Air Force stops at Prestwick and Turnberry, though he couldn’t help but note their “good taste” in staying at his flailing resort. This has more or less been his defense in other instances in which he’s been accused of profiting off taxpayers; in August he suggested the United States would host the next G7 in 2020 at Doral, citing his Florida club’s proximity to the airport and its “tremendous acreage.” The issue came up again just days later, when Pence stayed at Trump’s Doonbeg resort in Ireland—despite the club being 180 miles away from his diplomatic meetings in Dublin. At the time, a person close to the president told CNN that Trump was “irked” by the negative press and cited his “genuine belief that his locations are the best place for aides to lodge.”

Pence, too, swatted away suggestions that Trump directed him to stay at Doonbeg. Still, the House Oversight Committee is investigating the matter. “The Committee does not believe that U.S. taxpayer funds should be used to personally enrich President Trump, his family, and his companies,” Cummings, the chairman, wrote to the vice president’s office.

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