The Defense Department defended Wednesday the project to replace Air Force One, the flagship plane used by US presidents, a day after President-elect Donald Trump called the project's costs "ridiculous."

Boeing has received a $170 million contract to develop the scope and requirements of replacing the aging Air Force One, which is actually two planes — one for the president and a spare.

On Tuesday, Trump said Boeing was spending $4 billion on the new plane and called for the order to be canceled.

Converting a pair of 747-8 jumbo jets to state-of-the-art luxury command centers by 2024 had been estimated to cost $3 billion, and cost overruns and delays could bring the price tag up to Trump's estimate.

But Pentagon spokesman Navy Captain Jeff Davis underscored the complexities of the project and suggested it was not a simple bonanza for Boeing.

"It sounds like a lot, but you have to remember: This is a system of systems, it's multiple aircraft and it's not all Boeing," Davis said.

"This is a system that's going to have many different companies providing the systems that go on it. And we simply don't know the exact figure."

Trump's comments on the project briefly had pulled Boeing's stock price lower but it has recovered amid a broader market rally.

Aside from being a luxury command center for the president, Air Force One is packed with defensive capabilities, missile-evasion technologies and communications platforms.

"They have tremendous capabilities both in terms of communication, how they are hardened and their defenses and how they can employ onboard systems to defend themselves in all sorts of situations that we can think of," Davis said.

"We look forward to the opportunity to explain the specific requirements… (and) the current estimate, and we are prepared to work with the new president and the new administration to further reduce costs."

Boeing promises Trump to control costs on Air Force One
New York (AFP) Dec 7, 2016 –

Boeing has pledged to control costs on the redesign of Air Force One after President-elect Donald Trump blasted the aerospace giant for the ballooning expenses, a company spokesman said Wednesday.

Boeing chief executive Dennis Muilenburg reassured Trump in a phone call Tuesday night about its commitment to keeping a tight rein on costs for the presidential plane, after the president-elect earlier in the day tweeted that the price tag was "out of control."

"Muilenburg congratulated Mr. Trump on his election win and committed to working with the new administration to control costs as they establish requirements for the new Air Force One to keep the program as affordable as possible and deliver the best value to American taxpayers," a Boeing spokesman told AFP.

Muilenburg's conversation with the president-elect came after Trump took to Twitter Tuesday morning and threatened to cancel the Air Force One contract, saying costs had ballooned to $4 billion.

Boeing has not directly addressed Trump's statement, but said Tuesday it has a $170 million contract "to help determine the capabilities of these complex military aircraft that serve the unique requirements of the President of the United States."

Trump took a tough line with Boeing, as he has with other companies that draw his ire.

"If we don't get the prices down, we're not going to order them, we'll stay with what we have." the president-elect told the "Today" show broadcast Wednesday morning.

The legendary Air Force One jets — light blue and white liveried, with "United States of America" emblazoned on the fuselage and an American flag on the tail — are a powerful symbol of US might, but the current models are nearing the end of their 30-year lifespan.

The planes are equipped with numerous security and defensive measures, most of which are top secret, as well as the ability to refuel in flight.

Though he has frequently singled out particular companies for criticism, Trump's latest attack-by-tweet came an hour after the Chicago Tribune posted an article on its website quoting Muilenburg expressing concern about the president-elect's protectionist bent, and noting the firm's growing business with China.

It was unclear if Trump was aware of Muilenburg's comments before his outburst, but several US media were raising the possibility of a connection.