The United States has officially accepted a Boeing 747-8 luxury jetliner as a gift from the Qatari government, and the Air Force has been tasked with upgrading it to be used as a new plane for President Trump, according to an Air Force spokesperson.

The spokesperson, who spoke on the condition of anonymity as they were not authorized to speak publicly about the matter, told NPR that the Air Force is currently "preparing to award a contract to modify a Boeing 747 aircraft for an executive airlift," saying further details about the contract are classified.

The plane ? worth hundreds of millions of dollars ? is a gift that Trump said he would be "stupid" to turn down, suggesting that it could be converted quickly to be ready for use as the presidential aircraft.

But experts warn that no matter how luxurious the plane is, it would take years to rework it to meet the current standards set for Air Force One.

Democratic lawmakers and independent watchdogs say the gift violates the Constitution's Foreign Emoluments Clause.

The White House said the plane was a gift to the Department of Defense, and would go through the legal protocols required when something is given to the government. Trump has said he would not use it after leaving office and wants to keep it in his presidential library at that point.

There are currently two new Boeing 747-8 planes being customized to become the next generation of Air Force One. Trump announced a $3.9 billion deal with Boeing during his first term for the project. The planes were supposed to be ready by last year, but the project has been marred by setbacks, and now the customized aircraft aren't expected for several more years.

"Some of that is due to poor execution. But some of that is just due to the huge amount of requirements and work needed to take a commercial jet and wire it up," for the extensive security measures standard in Air Force One planes, said Richard Aboulafia, managing director of AeroDynamic Advisory and an aviation analyst, speaking to NPR's Morning Edition.

He called Trump's plan for the plane from Qatar to be converted quickly a "fantasy."

The current Air Force One fleet has been in use for over three decades

Technically, "Air Force One" is the call signal used for any plane carrying the president of the United States. But more commonly it's used to refer to the specific specialized planes ? currently Boeing 747-200B models ? outfitted with state-of-the-art communications and defense systems, along with lots of other (often highly classified) features.

The two Boeing planes currently serving as Air Force One have been in operation since 1990. A plan to replace them has been in the works for years, with Boeing winning the contract back in 2016 under then-President Obama.

"It's a mobile White House," says Doug Birkey, executive director of the Mitchell Institute for Aerospace Studies. "All the functions of the president have to be executed in it, no matter what circumstances, including warfare."

Birkey says that includes requiring an "incredibly robust command and control suite" and defenses against anything from surface-to-air missiles to a nuclear blast and warfare.

He says in terms of luxury, the plane from Qatar probably looks and feels better than the current or planned Air Force One planes ? but it's unlikely that it has any of the communications or defense systems needed.

"And installing those is not an easy thing. I mean, you have to deconstruct the aircraft a fair amount to do that," Birkey says.

Trump has repeatedly stressed that the plane from Qatar was free, but several experts NPR talked to agreed that it will likely end up costing a significant amount of money ? up to a billion dollars by Aboulafia's estimate ? to outfit it properly to current standards to become Air Force One.

A U.S. official who requested anonymity because they weren't authorized to speak publicly about the matter told NPR the conversion would likely cost hundreds of millions of dollars. (VPM)

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