President Trump on Monday denied knowing about, or having anything to do with, an Air Force aircrew’s stay at a golf resort he owns in Scotland earlier this year.

And the Air Force has ordered Air Mobility Command to review its guidance on how airports and lodging accommodations are selected during international travel. The announcement came as controversy grew over the C-17 Globemaster III crew’s stay at Trump’s Turnberry resort near Glasgow in March, and the House Oversight Committee is reviewing the stop as part of a broader investigation into the military’s spending at and around Turnberry. The crew was on its way from Joint Base Elmendorf-Richards in Alaska to Kuwait at the time.

Politico first reported on the aircrew’s Turnberry stay, and the Air Force’s review of its travel practices.

Trump posted a Tweet Monday morning in which he said he knows nothing about the C-17 crew landing at the Prestwick Airport, or about the crew’s overnight stay at Turnberry ― though he added in a parenthetical “they have good taste!”

A few minutes later, Trump tweeted a similar denial of involvement with Vice President Mike Pence’s decision last month to stay at a Trump-owned resort in Doonbeg, Ireland, which has also become controversial.

Critics are questioning whether it is appropriate and ethical for government officials and military service members on official travel to stay at hotels owned by the president, and whether it represents an improper steering of taxpayer dollars to Trump’s business ventures.

In an email Monday, Air Force Public Affairs Director Brig. Gen. Ed Thomas said that Air Force leadership has ordered the review of AMC international travel guidelines, though he said “the review is not about Trump properties.”

“While initial reviews indicate that aircrew transiting through Scotland adhered to all guidance and procedures, we understand the U.S. service members lodging at higher-end accommodations, even if within government rates, might be allowable but not advisable,” Thomas said. “Therefore, we are reviewing all associated guidance. Even when USAF aircrews follow all directives and guidance, we must still be considerate of perceptions of not being good stewards of taxpayer funds that might be created through the appearance of aircrew staying at such locations.”

Thomas said the review will cover travel for active duty, Guard and Reserve airmen.

Thomas also said that Air Force mobility aircraft, particularly C-17 Globemasters, have increasingly used Prestwick as a stopover since 2015 for several reasons. Its round-the-clock operations make it a good option for aircraft traveling to and from the U.S. Central Command area of responsibility, or the Middle East, he said.

AMC also in 2017 ordered mobility crews to standardize routing locations as a way to increase efficiencies, Thomas said, and Prestwick was one of the top five locations recommended. Its weather is more favorable than Shannon Airport in Western Ireland, Thomas said, and there is typically less aircraft parking congestion than locations in the European continent that handle AMC’s high-priority mobility aircraft missions.

“By considering factors like these to save costs and increase operational efficiencies, Air Operations Center contingency planners have increasingly turned to Prestwick to develop route plans for lower-priority contingency needs such as training, deploy/redeploy and Guard airlift missions,” Thomas said.

AMC aircraft have stopped at Prestwick 936 times since 2015, including 659 overnight stays, Thomas said. The number of annual stops there have increased steadily each year, from 95 in 2015 to 145 in 2016, then to 180 in 2017, and 257 in 2018. There have also been 259 Prestwick stops in 2019, through August.

Overnight stays similarly increased annually, from 40 in 2015 to 75 in 2016, to 116 in 2017, to 208 in 2018, and 220 so far in 2019. Military.com’s Oriana Pawlyk first reported those statistics on Twitter.

Thomas said that military locations can frequently be unavailable for mobility aircraft en route to international locations, requiring them to stop at civilian airfields. A military location may not be operating at the time the transiting aircraft needs to stop, he said, or that military airfield may be “filled up” with other aircraft parked or being serviced there.

That’s why the Defense Department arranges to use civilian airfields, particularly locations that are open around-the-clock, have plenty of parking to handle large aircraft or large numbers of aircraft, and are geographically located near common flight routes, Thomas said. And when the military chooses one of those airfields, it negotiates fuel prices to obtain the best rate it can.

That’s what the military has done with Prestwick, Thomas said, which has a large parking area, is open 365 days a year at all hours, and is along the route to and from Europe and the Middle East.

“When military airfields are unavailable, USAF aircrews are then directed to select one of these locations for transit,” Thomas said. “This is standard practice used at select civil airfields around the world. ... Bottom line, the availability of civil airfields like Prestwick is essential to ensuring that USAF aircraft can sustain the necessary speed and throughput required to accomplish our mission.”

Thomas also said that aircrews typically try to stay on-site at military airfields during overnight stops, though sometimes lodging there is filled up and they must find nearby hotel rooms elsewhere.

In those cases, and in instances when a crew stops at a civil airfield, the crews are required to find rooms that do not exceed per diem cost limits, are reasonably near the airfield, and are suitable, Thomas said. Sometimes, aircrews require rooms with black-out blinds to allow them to sleep during the daytime, if their mission requires it.

Usually, there are multiple lodging options near civil airfields that crews can use, Thomas said, which helps keep costs down. But in some less-populated areas, lodging options are further away and can sometimes take an hour or more to get there, he said.

And sometimes, Thomas said, the lodging options for aircrew include higher-end hotels. It’s fine for crews to stay at those higher-end places, he said, as long as the location is suitable and it’s within DoD’s allowed rate.

The Air Force said the nightly rate at the Turnberry hotel was $136 during the crew’s stay, which was less than the maximum per diem rate of $166. When the crew stopped at Prestwick on their way back from Kuwait, the Air Force said it stayed at a nearby Marriott hotel that cost $161 a night.