The military's increasing use of the struggling hotel is also part of a broader investigation by the House Oversight Committee into whether the president has violated the emoluments clause of the Constitution by benefiting financially while in office.

One leading Democrat is already calling the Air Force review, released Friday, insufficient and is demanding a more independent investigation of military spending at Trump properties.

“We know there is smoke, and the report’s data is so incomplete and misleading, I can only conclude that there is fire," Sen. Richard Blumenthal (D-Conn.), a member of the Armed Services Committee, said in a statement, calling the report “stunningly inadequate.”

“The Air Force inspector general must open an immediate investigation to acquire the full accounting of taxpayers' dollars spent at Trump Turnberry — and how much that spending has increased since President Trump took office," Blumenthal said. "At the same time, the Department of Defense inspector general should begin investigating illegal spending at Trump properties by every military service."

Meanwhile, Sen. Gary Peters (D-Mich.), who previously requested that the Pentagon Inspector General open up its own probe, told POLITICO he believes "taxpayers have a right to know whether our armed forces are making decisions based on operational concerns or the President’s private businesses" and "this report has not answered that key question."

"I will continue pressing for an independent investigation to determine whether the Air Force misused taxpayer dollars at the President’s private resort," Peters added in a statement.

The Air Force report, however, concluded there has been no wrongdoing.

"This review found that existing guidance, and the processes used to apply that guidance, are sufficient," according to the 34-page Air Force report. "However, the team concluded that educating aircrew on applicable regulations is a continuous process and [Air Mobility Command] can improve how it educates aircrew on travel regulations by incorporating lessons and discussion items into its aircraft commander training."

"Although the review found no instances of inappropriate decision-making by aircrews transiting Prestwick Airport and lodging in the local areas," the report concluded, "the broad nature of existing guidance suggests some additional focused training would be of value to affirm the role of the aircrew in the process."

President Donald Trump gives a press conference at his Trump Turnberry Resort in June 2016. | Jeff J Mitchell/Getty Images

It further stipulated the broad guidance currently in place "also requires those who make decisions about lodging to use sound judgment and reasoning, weighing multiple different criteria to make an informed decision based on the known conditions at the time."

Of all the refueling stops over the last five years at Prestwick, where the U.S. military has a contract for refueling services, 77 percent, or 419 aircrews, stayed in hotels in the local Prestwick area. Some 17 percent, or 95 aircrews, stayed in hotels in Glasgow. And 6 percent, or 31 aircrews, stayed at the Turnberry resort, the report found.

It also detailed six instances when aircrews stayed longer than 24 hours at Turnberry.

"For five of those six aircrews," the Air Force found, "their aircraft had maintenance issues that required repair. The sixth aircrew was delayed for operational reasons."

"The distribution is consistent with policy and guidance for selecting aircrew accommodations — and when aircrew are billeted outside the local Prestwick area, the distribution does not indicate a preference for any particular location," according to the report.

Even so, the review is unlikely to satisfy many congressional Democrats.

“The report utterly fails to address the many questions I have raised about the number and duration of stays by airmen at President Trump’s personal resort, allowing him to use our military budget as his personal piggy bank,” Blumenthal said in his statement.

“From what little information is provided," he added, "it appears the number of stays at Trump’s Turnberry resort dramatically increased as he became president — but the report glaringly omits exactly how much those stays increased and how much money has flowed from the Air Force to line Trump’s pockets.”

“Most egregiously," he concluded, "the report fails to include whether the Air Force has taken appropriate steps to prevent illegal payments and therefore provides no guidance on how the Air Force should adhere to the Constitution.”

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In most cases, the Air Force found the accommodations were made on the crews' behalf by various government agencies through the Defense Department's worldwide travel system.

"However, the aircraft commander is the last link in the decision chain to ensure lodging arrangements are appropriate," the report noted, including taking into account availability, suitability, expense and proximity.

"Formally training new aircraft commanders to consider these four criteria will enhance knowledge at the aircrew level and continue to ensure commercial lodging of transient aircrew, when required, is consistent with the appropriate use of government resources while fulfilling operational mission requirements in a safe and professional manner," the report said.

Still, Blumenthal insisted a much more comprehensive look is still needed.

"Turnberry is one resort and the Air Force is one service — how many other Trump hotels have Pentagon service members and civilians stayed at, and how many taxpayer dollars have been improperly spent there?” he asked.

Last month Peters enlisted more than 30 other senators in introducing the HOTEL Act, which would bar taxpayer funding from being used at all Trump-owned properties.

Connor O'Brien contributed to this report.