WASHINGTON, June 5 (Reuters) - It will cost hundreds of

millions of dollars to retrofit a Qatari luxury Boeing 747

jetliner to fly as the new Air Force One, Air Force Secretary

Troy Meink said on Thursday.

Last month, the U.S. military accepted the gift from Qatar

to transport U.S. President Donald Trump.

Retrofitting the 13-year-old plane, which has a luxurious

interior, will require significant security upgrades,

communications improvements to prevent spies from listening in

and the ability to fend off incoming missiles, experts say.

"It's probably less than $400 million to retrofit that

aircraft," Meink told lawmakers during a Congressional hearing.

Democratic lawmakers have said it could cost more than $1

billion to retrofit the plane.

Meink said a lot of those costs are ones the Air Force would

have experienced anyway.

"I think there has been a number thrown around, on the order

of a billion dollars, but a lot of those costs associated with

that are costs that we would've experienced anyway," he said,

adding that this included buying additional platforms for

training and spares.

Legal experts have questioned the scope of laws relating to

gifts from foreign governments that aim to thwart corruption and

improper influence. Democrats have also sought to block the

handover.

Qatar has dismissed concerns about the aircraft deal. Trump

has also shrugged off ethical concerns, saying it would be

"stupid" not to accept the 747-8 jet.

The Air Force One program has faced chronic delays over the

last decade, with the delivery of two new 747-8s slated for

2027, three years behind the previous schedule.

Trump toured the Qatari Boeing plane in February at a

Florida airport.