President Donald Trump reportedly secretly traveled on a smaller military plane, rather than Air Force One, because of the threat of an Iranian assassination plot as he left the NATO summit in Ankara, Turkey, last month, piling fresh attention on the safety and security status of presidential transport.

The president was seen embarking Air Force One in the Turkish capital, but was then smuggled onto an alternative plane, an Air Force C-32A, in a catering truck used to bring meals onboard an aircraft, The Washington Post reported on Monday.

This essentially made Air Force One, and the White House staff strapped in next to journalists, a decoy. Newsweek has reached out to the White House and Secret Service for comment via email.

Trump had announced ahead of the journey he would take the "former Air Force One" from the NATO summit to an airbase in the U.K. "for old time's sake," rather than travel on the controversial, Qatari-donated Boeing 747-8 jet.

Questions had swirled over the security status of the Qatari jet, which has been since modified by the U.S. military. It was unveiled by Trump at Joint Base Andrews in June, when the president said the aircraft boasted a "level of luxury that nobody's ever seen before."

What Is The Air Force's C-32A?

The C-32A is often used by the vice-president, the first lady, and senior politicians traveling around the globe. When they're on board, it uses the call sign Air Force Two.

The cabin, where passengers sit, is split up into four sections. One part has a communications center, ten seats, refreshment facilities and a toilet, while a second is a "fully-enclosed stateroom," the U.S. Air Force says. Within this, there is a changing area, an entertainment system, a fold-out bed, another toilet and two first-class seats.

Another eight seats are located in a third section of the plane, while a further 32 seats, a galley, and two toilets are positioned at the back.

How Does Air Force One Compare?

The current Air Force One fleet is made up of two, specially-configured Boeing 747-200B aircraft, known as VC-25.

The interior of the commercial airliner has been changed, and the aircraft has been fitted with advanced avionics, according to the Air Force.

The C-32 is much smaller than the VC-25, which is set up to be a flying command center for the president and his staff.

But because the C-32 is a military aircraft—an upgraded version of the Boeing 757-200, regularly used by the vice president and other top U.S. officials—security is a top priority.

The C-32 is built so it's easier for those onboard to see around and underneath the aircraft, to more quickly detect any threats to the plane and its passengers, the military says.

Many of the security and defense systems built into both aircraft aren't public knowledge. The Air Force says the C-32 has systems built in that alert the crew to any possible threats to the aircraft from the air and ground in advance, as well as sophisticated navigation systems and information to make sure it doesn't collide mid-air with another aircraft.

But the roughly $400 million jet donated by Qatar was criticized for not having many of the defense measures presidential transport typically does, like technology that pushes away heat-seeking missiles heading for the jet.

The C-32s and VC-25s have been in service for decades, and replacement Boeing jets are in the works and expected to be handed over by roughly 2028.

Contact Newsweek editors on this story: Ben Kelly and Cristina Diciu.