The House Oversight and Government Reform Committee has opened an investigation into the matter.
The US Air Force said in a statement Saturday that its crews did stay at President Donald Trump's luxury golf resort in Scotland, but that it was "the closest available and least expensive" option. "In this case, they made reservations through the Defence Travel System and used the closest available and least expensive accommodations to the airfield within the crews' allowable hotel rates".
Citing Defence Logistics Agency (DLA) records, it said the USA military had made 629 fuel purchase orders at the airport, totalling $11m (£9m), since October 2017. The letter also cited a Guardian report from February of a year ago that the airport provided reduced rate rooms and free rounds of golf for USA military and civilian air crews.
The committee's accusations are detailed in a letter to the Pentagon - which is dated to June but was only revealed on the Politico website on Friday.
Home Democrats are additionally presently investigating Vice President Mike Pence's keep per week in the past at Trump's golf resort in Doonbeg, Eire, claiming the choice might have violated the Structure's emoluments clause.
The mission in question began at Joint Base Elmendorf-Richardson, Alaska on March 13, and included stops at Creech Air Force Base, Nevada; Portsmouth International Airport at Pease, New Hampshire, a dual civilian-military airport; Prestwick; and Ali Al Salem Air Base in Kuwait, Thomas said.More news: Vivaldi Browser Now Available on Android
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"The stopover of a U.S. Air Force C-17 in Glasgow, Scotland, is not unusual", Brig Gen. Ed Thomas said in an email.
"The Defense Department has not produced a single document in this investigation", a senior Democratic aide told Politico.
A powerful House of Representatives panel could soon step up pressure on the Pentagon for documents about an airport near a Trump-owned golf course in Scotland that has benefited from USA military purchases since President Donald Trump took office, an aide said on Saturday.
The House Oversight letter, mentioning the Washington Post, says declines at Trump's Scottish hotel amounted to $4.5 million in 2017.
Trump resigned as director of Turnberry when he took office in January 2017 but continues to hold an ownership stake.
Both Trump Turnberry and the airport have operated at significant losses in recent years, with the Scottish government putting Prestwick up for sale after taking it into public ownership in 2013.