According to an unnamed US official cited by the newspaper, Trump boarded Air Force One in Ankara on July 8 after attending a NATO summit. He was then moved through a catering container attached to the aircraft and transferred to a smaller C-32A plane, which flew him to Britain.
The operation was reportedly kept secret, with journalists and some officials led to believe that Trump remained aboard the larger Boeing 747.
The reported security measure came amid concerns over a possible attack by Iranian proxy groups. US media had previously reported that an Iranian threat was behind the decision to prevent Trump from departing Turkey aboard the new Boeing 747-8 gifted to the United States by Qatar.
At the time, Trump said he would use the older Boeing 747 so that US military personnel at an airbase in Britain could tour the new aircraft.
However, several US media outlets, including The New York Times, reported that the aircraft switch was prompted by security concerns linked to Iran.
Journalists travelling aboard the older Air Force One were also instructed to keep their window blinds closed, a measure normally associated with flights through conflict zones.
The incident has renewed scrutiny of the Qatar-gifted aircraft, which reportedly lacks some of the defensive systems installed on the older presidential aircraft, including anti-missile capabilities.
Qatar's royal family donated the luxury Boeing 747 to the United States last year after Trump criticised the two aging Boeing 747s that had served as Air Force One since 1990.
The aircraft was subsequently retrofitted and was first used by Trump on July 1 for a domestic trip to North Dakota. Days later, he took it on his first overseas journey to Turkey.
The White House defended the safety of the new aircraft when asked about the Washington Post report.
White House Communications Director Steven Cheung said the aircraft was equipped with "high-level security protocols" designed to protect the president and his staff.
He added that Trump faced threats from "many enemies of America" and that the administration was using every available measure to address them.
Video published by The Washington Post reportedly shows a catering truck lowering from the older Air Force One shortly after Trump boarded the aircraft in Ankara. The truck was then seen travelling toward the smaller C-32A aircraft.
Both planes later arrived in Britain. Trump was subsequently filmed disembarking from the larger aircraft and entering the newly retrofitted Air Force One.
It remains unclear how Trump was transferred back to the larger aircraft after arriving in Britain.
