(AP) – President Donald Trump secretly flew out of last month’s NATO summit in Ankara, Turkey, on an alternate military aircraft while the White House made it appear that the Republican president was flying on Air Force One, according to a report published by The Washington Post on Monday.

The Post said the operation was prompted by an Iranian assassination threat against Trump. The ruse was carried out as journalists and some White House staff members were led to believe they were on the same plane as the president as he began his journey back to Washington from the annual gathering of NATO country leaders.

The Post cited material reviewed by the newspaper, a U.S. official familiar with the operation and another person with knowledge of the president’s travel. The Associated Press has not independently confirmed the report.

Trump had flown to the summit in a new Qatari-gifted and retrofitted red, white and navy blue jet. But ahead of departing Turkey, he said he would fly partway home on an older-model baby blue Air Force One plane instead.

The president at the time said the new luxury jet was being flown out ahead of his departure from Ankara to give some U.S. troops based in Eastern England a chance to check out the new Air Force One.

In Ankara, Trump boarded the old Air Force One jumbo jet in view of television cameras ahead of the plane flying to Royal Air Force Mildenhall in the United Kingdom.

However, according to the Post report, after boarding the legacy Air Force One jet, he was secretly shuttled minutes later to a smaller plane — an Air Force C-32A — via an airport catering truck typically used to load meals and other supplies. Trump flew to Mildenhall on that smaller jet.

The White House did not respond directly to questions about the Post report of the secret operation to whisk Trump out of the country on a third aircraft, or the reported elaborate ruse to make it appear he was on the baby blue Air Force One jet flying to Mildenhall.

“As the President has said recently, there are many enemies of America who have their sights on him, and we use every tool at our disposal to address those threats,” White House communications director Steven Cheung said in a statement.

The U.S. Secret Service declined to comment. The Air Force, which maintains the fleet of executive travel aircraft, referred questions to the White House.

There have been questions about the safety of the new Qatari-gifted plane
While Trump was in Turkey, the U.S. military conducted a series of large strikes in Iran in retaliation for its attacks on merchant shipping in the region.

The New York Times and CBS News reported last month that intelligence officials had raised concerns about a potential attack on the president or his jet, triggering additional precautions and the decision not to use the newly inaugurated aircraft gifted to Trump by Qatar for the first leg of Trump’s trip home from Ankara.

The swap had spurred questions about the security of the Qatar-provided aircraft, and Trump said last month after the trip that it would undergo additional upgrades.

Cheung on Monday maintained that the new, Qatari-gifted plane was “a state-of-the-art aircraft that has been fitted with high-level security protocols that ensure the safety of the President and his staff.”

The new Post report on clandestinely putting Trump on a third aircraft and quietly whisking him out of the country adds a fresh layer to just how seriously concerned U.S. security officials were about the threat against Trump during the ongoing war with Iran.

Paul Eckloff, a former special agent with the Secret Service, said such an unusual move could either reflect actionable intelligence or an abundance of caution given volatility in the region with the wars in Iran and Ukraine.

“I would not say unprecedented, but it is an unusual occurrence,” said Eckloff.

The Post reported that to exit that plane without being seen by those uninvolved in the operation, Trump and several aides stepped aboard an airport catering truck, which was elevated planeside using hydraulics and positioned at a door on the opposite side of Air Force One’s entrance.

The small group of reporters who thought they were traveling with Trump were advised to lower their window shades ahead of takeoff.

After arriving at Mildenhall, news photographers captured images of Trump getting off the presidential plane — suggesting he reboarded Air Force One out of sight of the pack of journalists who thought they were traveling with him.

Democratic Sen. Richard Blumenthal called for a congressional investigation.

“It is unprecedented and it is surreal,” he said Monday on CNN, calling the incident “downright scary.”

After the brief visit to the base at Mildenhall, Trump boarded the new Air Force One aircraft to fly the rest of the way to Washington.

During a gaggle with reporters aboard the aircraft, Trump was asked directly if there was any credible threats on Air Force One by Iran.

“Well, I have a threat all the time. I’m number one on their list before you,” Trump said. He added to the traveling reporters, “But if I go, you go.”