The president-elect’s most recent financial disclosure form, filed in May and detailing his 2015 holdings, showed that the Manhattan billionaire owned between $50,001 and $100,000 worth of stock in Boeing, a purchase he announced on Twitter in 2013. Jason Miller, a spokesman for Trump, said Tuesday morning that had Trump sold all of his stocks last June.

Miller added that the exact details of Trump’s desire to cancel the Boeing order would be dealt with after he is inaugurated next month. But Trump’s comments, Miller said, “really speaks to the president-elect’s focus on keeping costs down across the board.”

Trump’s surprise rebuke of Boeing’s presidential aircraft project came on the heels of a private-sector victory of sorts for the president-elect: his team’s successful negotiation with Carrier Air Conditioning to keep several hundred jobs in Indiana that had previously been slated to move to Mexico. The two very public interactions with private corporations, albeit ones who do significant business with the federal government, are early indicators that Trump seems intent on bringing his aggressive deal-making style with him to the White House.

Trump has thus far not shied away from breaking president-elect protocol in other ways too: He spoke on the phone late last week with the president of Taiwan, the first known communication between a Taiwanese leader and U.S. president or president-elect since 1979. Trump did not communicate with the State Department before taking the call, something past presidents-elect have done in similarly contentious situations, a department spokesman said Monday.

Trump’s tweet came just 22 minutes after the Chicago Tribune published comments by Boeing CEO Dennis Muilenburg, who said he worried that Trump’s promises of a more protectionist trade policy could hurt his company, which does robust business with China. Muilenburg told the Tribune that he would urge the president-elect to take a warmer stance toward the kinds of trade deals he railed against on the campaign trail, warning, “If we do not lead when it comes to writing these rules, our competitors will write them for us.”

Boeing stock slumped Tuesday morning in the wake of the president-elect’s remark, but rebounded somewhat as the morning progressed.

The Air Force said previously that it had earmarked $1.65 billion for two new presidential aircraft, which will be four-engine Boeing 747-8s. The source of Trump’s $4 billion cost estimate for the program was not immediately clear, although a Government Accountability Office report from last March priced it at roughly $3.2 billion.

The two planes are so expensive, Air Force Secretary Deborah Lee James said, because of the added features demanded by White House security personnel. Air Force One is “a flying White House, in terms of the security,” she said, noting that the new aircraft would be able to defend itself against missile attacks and give the president the ability to communicate with nuclear forces and allow him or her to run the government for extended periods of time if need be.

James said the experts offering the recommendations for the next generation Air Force One are “not political appointees. They are professional security people.”

“Air Force One, although it is a 747 platform, is way, way more than what you would think of as a commercial airliner,” the Air Force secretary said. “This is carrying the president of the United States. It has to go long distances, it has to survive under difficult circumstances, much more difficulty than a normal civilian airliner. So it is a bit more complicated than perhaps meets the eye.”

The Pentagon announced the deal with Boeing last January, awarding an initial contract worth nearly $26 million for initial research for the new planes, according to Reuters. The Defense Department awarded an additional $127.3 million contract in July to develop interior, power and electronic specifications for the next-generation aircraft, according to FlightGlobal, a publication that covers the aviation industry.

“We are currently under contract for $170 million to help determine the capabilities of these complex military aircraft that serve the unique requirements of the President of the United States,” Boeing said in a statement released Tuesday morning. “We look forward to working with the U.S. Air Force on subsequent phases of the program allowing us to deliver the best planes for the president at the best value for the American taxpayer.”

Speaking aboard the current Air Force One during President Barack Obama’s trip to MacDill Air Force Base, where he will speak to U.S. Central Command, White House Press Secretary Josh Earnest questioned Trump’s $4 billion figure. “Some of the statistics that have been, uh, cited, shall we say, don’t appear to reflect the nature of the financial agreement between Boeing and the Department of Defense,” he said.

Aircraft in the presidential fleet have “unique technical requirements,” Earnest said, adding that “the American people would expect that future U.S. presidents would benefit from unique and upgraded capabilities while they are traveling and representing the interests of the United States around the world.” He noted that the plane on which he and the president and the traveling pool were currently flying is “nearing the end of its projected life.”

In addition to the presidential aircraft that Trump will fly on as president, the Manhattan billionaire maintains a personal fleet that includes two planes and three helicopters. The New York Times reported last April that four of Trump’s five aircraft are more than 20 years old, which is rare for someone of the president-elect’s wealth. According to the Times, Trump’s largest, and favorite, aircraft from the fleet is his 1991 Boeing 757, which has brushed 24-karat gold fixtures and leather toilet seats.

President Barack Obama voiced a similar concern shortly after taking office in 2009, when Reuters reported that he told a group of lawmakers that costs for a Lockheed-Martin program to replace the presidential helicopter fleet had “gone amok.” He told that group, gathered at the White House, that reining in military spending would be “one of our highest priorities” and added that “the helicopter I have now seems perfectly adequate to me.”

Asked how Obama’s concerns about the Lockheed-Martin contract differed from Trump’s regarding the presidential planes, Earnest said the helicopter program was much further along that Boeing’s is now and had costs that had far overrun what was originally expected. He also noted that Obama raised his concerns about the helicopter program’s costs at a “historically difficult” time for the U.S. economy, which was mired in recession.

Obama ultimately asked the Pentagon to revisit the program and find a way to better control costs, Earnest said. The press secretary added, “I expect that that effective management of that program will result in a new presidential helicopter that President-elect Trump will be glad that he has.”