The jet Qatar gave Trump is valued around $400 million. It might cost taxpayers $1 billion just to upgrade it to presidential standards

• The Boeing 747 Qatar donated to the Air Force One fleet costs roughly $400 million when new, but outfitting the jet to fit presidential requirements may cost up to $1 billion, according to experts. The Qataris have had trouble trying to sell the aircraft as 747s have fallen out of popularity within the aviation industry and are no longer manufactured. 

While President Donald Trump flaunts his $400 million Qatari airplane, touted to be the newest member of the Air Force One fleet, experts say it could cost $1 billion just to bring the jet up to presidential standards. 

In addition to ethical concerns over the Qatari-owned Boeing 747 becoming the largest foreign gift ever received by the U.S. government, Sen. Tammy Duckworth said the jet could also cost up to 10 figures in taxpayer dollars to operate within the Air Force One fleet. 

“Far from saving money, this unconstitutional action will not only cost our nation its dignity, but it will force taxpayers to waste over a billion dollars to overhaul this particular aircraft, when we currently have not one, but two fully operational and fully capable Air Force One aircraft,” the Illinois Democrat said in a statement to multiple outlets.

One expert puts that figure higher: Richard Aboulafia, a managing director at aviation consulting firm AeroDynamic Advisory, said converting the aircraft into an Air Force One jet would cost billions and take years. 

“You’re taking a 747, disassembling it, reassembling it, and then jacking it up to a very high level,” Aboulafia told NBC News.

In order to secure the jet for presidential use, it would have to be examined for any listening devices and outfitted with communications equipment and missile defense systems. These costs would accumulate at least $1 billion, current and former Pentagon officials told The New York Times.

White House officials have said the government is looking into partnering with government contractor L3Harris to maintain the jet, the Times reported. The cost of the reported deal has not been public. 

L3Harris declined Fortune’s request for comment.

As the jet’s upgrades will take a couple years, the government has already paid Boeing for two new Air Force One jets projected to be completed by 2027. 

“That’s a better dollar value than trying to take an airplane from somebody else and trying to make it into a presidential plane. It makes no sense,” Marc Foulkrod, an aerospace engineer who had tried to help Doha sell the jet, told The New York Times.

Meanwhile, the price tag for a crew on a traditional Air Force One jet reaches more than $37 million annually, while the total operating cost sits at roughly $134 million per year, according to Pentagon documents.

A White House spokesperson said, “It has been stated time and time and time and time again this was donated as a gift to the DoD and the Air Force” and referred Fortune to the DoD for further comment. The DoD declined to comment.

Prior to offering the jet to the U.S., the Qataris had been unsuccessful in finding a suitor for the Boeing 747. Foulkrod said while the plane is in great condition, it’s hard to find a buyer for a VIP styled-aircraft. 

“You might find that one-off guy that has a super ego that wants to buy one and ride around in it,” Foulkrod said.

Commercial airlines lacked interest in the jet because 747s are no longer manufactured and are falling out of popularity among the aviation industry, and the jet was too lavishly outfitted to be suitable for commercial use.

This story was originally featured on Fortune.com