ANKARA — President Donald Trump departed a NATO summit in Turkey last month by secretly boarding a smaller Air Force jet, a Boeing C-32A, using an airport catering truck to transfer from a decoy aircraft. U.S. officials considered the assassination threat from Iran against the president to be serious.

Trump was widely believed to have left Ankara on one of the larger Boeing 747s designated as Air Force One. He was not on either of the two 747 aircraft available. The C-32A flew him to the United Kingdom for the first leg of his journey.

The deception involved Trump and several aides appearing to board an older 747 Air Force One in front of cameras. They then stepped into a catering truck, hydraulically lifted to the plane's height on the opposite side, away from where reporters were positioned.

Journalists aboard the older 747, which still used the Air Force One call sign, reported that Trump was not seen during the flight from Ankara. Reporters were also asked to close their window blinds, an unusual request for such flights.

Trump later rejoined reporters and the rest of his staff on the second leg of the flight back to Washington. He initially denied any security concerns involving Iran, saying the plane swap was to allow a newly gifted Qatari 747 to visit a U.S. military base in Britain for troops to view the jet.

Under subsequent questioning, Trump acknowledged a persistent threat from Iran against his life. He said reporters were asked to close their blinds because they were "probably on a dangerous flight because of the sleazebags that we have to deal with."

White House communications director Steven Cheung did not deny the secret plane swap when asked for comment. Cheung defended the security features of the Qatari jet. "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," Cheung said.

Later last month, U.S. officials determined a credible threat against Trump existed from Iranian proxy forces. Those forces were reportedly targeting both the president and Air Force One. The Qatari 747 lacks certain security features present on the older plane.

The Qatari-gifted aircraft is expected to be taken out of service in the coming months for upgrades to enhance its security and operational capabilities. Hostilities between the United States and Iran had subsided when Trump departed Washington for the NATO summit but resumed during his time in Turkey.