The House Oversight and Reform Committee said that expenditure at the Prestwick airport has "increased substantially" since Trump came into office, the BBC reported on Saturday.
The debt-ridden airport, south of Glasgow and approximately 30 km north of Trump Turnberry, has been fighting off closure. It is said to be integral to the Trump business, which is also loss-making.
The Scottish government bought the airport in 2013, when it was facing closure. In June, it was put up for sale with no buyer announced till date.
The Committee's accusations were detailed in a letter, signed by the Democratic committee chairman Elijah Cummings, to the Pentagon which is dated to June but was only revealed on the Politico news website on Friday.
It requests access to all communications between the US Department of Defence and Trump Turnberry, as well as any related financial records.
Citing Defence Logistics Agency (DLA) records, it said the US military had made 629 fuel purchase orders at the airport, totalling $11 million since October 2017.
It also alleges that certain military personnel have been offered "cut-price rooms" and free rounds of golf at the Trump Turnberry resort.
"Given the President's continued financial stake in his Scotland golf courses, these reports raise questions about the president's potential receipt of US or foreign government emoluments in violation of the US Constitution and raise other serious conflict of interest concerns."
According to US media reports, the Department has not yet complied with the demands, the BBC said.
It has also not commented directly, and neither has the Trump Organisation.
( With inputs from IANS )