Tuesday morning, President-Elect Donald Trump sent out a tweet expressing dismay at the cost of the ongoing process to build a new pair of planes to serve as Air Force One. (Perhaps not coincidentally, this was shortly after Boeing's CEO expressed concerns about Trump's trade policy.)

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Boeing is building a brand new 747 Air Force One for future presidents, but costs are out of control, more than $4 billion. Cancel order! — Donald J. Trump (@realDonaldTrump) December 6, 2016

Trump spokesman Jason Miller expanded on the statement during a call with reporters. Per the Washington Post:

"I think this really speaks to the president-elect's focus on keeping costs down across the board with regard to government spending. I think people are really frustrated with some of the big price tags that are coming out for programs, even in addition to this one. So we're going to look for areas where we can keep costs down and look for ways where we can save money."

That $4 billion number is fuzzy at best. As Boeing has pointed out in a statement, the company is only under contract for $170 million currently, and the Air Force has earmarked $1.65 billion for the project. The Government Accountability Office, meanwhile, has estimated a total cost of $3.21 billion.

Now set those numbers aside for a second, because here's the other thing: The President's plane does need to be replaced. So halting the current project because it's too expensive really only makes sense if a cheaper, more practical solution exists.

Let's run through the various options.

Option 1: Continue flying the current planes indefinitely

"Air Force One" is merely a callsign for the plane the president is currently on, but two airplanes take on this name most frequently. Both are Boeing VC-25s—a specially outfitted version of the Boeing 747-200B. Both are very old.

The 747-200B was launched in 1971, but the pair currently serving the POTUS was first flown in 1987, four years before Boeing stopped production on the model altogether. Over the years, the two planes have been upgraded repeatedly to keep up with the times and to incorporate the latest communication and defense technology. The problem with the aging jets is simpler than that: it's the keeping-them-up-in-the-air technology.

"Spare parts are becoming difficult to obtain"

"Spare parts are becoming difficult to obtain," Joe Hagin, former deputy chief of staff to George W. Bush, told Popular Mechanics back in 2009. "[The] few 747-200s still flying today are in freighter service or operating in small overseas airlines." Parts that are no longer in active production need to be salvaged or custom made, meaning repairs take a long time, are extremely expensive, or both. That problem hasn't gotten any better in the seven years since, and there is no reason to believe the problem won't get worse.

Replacement craft were initially planned for 2017, and there was fear that even that was not soon enough. "There is a concern in some quarters within the Air Force that they really need the replacement much sooner," Hagin said back in '09. Now, the replacement Boeing 747-8s are expected to enter service by 2023 at the earliest. That's already an additional six years of high-expense operation.

It's unlikely this fact is lost on Trump, who said the following at rally in North Carolina this past July:

"Now Air Force One is a very old Boeing 747. It sucks up a lot of gas. A lot of fuel. Boy, the fuel bill. You turn on those engines, I can tell you, it's a lot of money."

The old planes will have to be replaced sooner or later, and "later" offers no practical benefits.

Option 2: Attempt to find a better, cheaper replacement

If Air Force One needs to be replaced—and quickly—is there a better option than the current Boeing project? Not really. When the Air Force chose Boeing to build the replacement planes for Air Force One back in January of 2015, there was no competition. That's because Boeing's 747-8 is effectively the only option that fits the bill. As the Air Force put it, it's the only U.S.-made plane "that when fully missionized meets the necessary critically important capabilities."

The 747-8 is the only plane that "meets the necessary critically important capabilities."

The only other plane that can live up to the Air Force's high requirements—which include a minimum of four engines and capability for in-air refueling, among a litany of other features—is the French-made Airbus A380. Complications of using a foreign-made plane aside, Airbus expressed disinterest in making a bid.

Worse yet, Boeing is scaling down its production of the 747 even with the Air Force One deal in place, and preparing to end production of new 747 jets altogether in the face of declining demand. So, new 747-8s may be a limited-time offer.

And there's not much reason to believe something better will come along. The air travel economy is trending towards nonstop flights and smaller jets. Boeing's future probably looks more like the two-engine 737 MAX than the giant 747-8, and size is crucial for Air Force One, given the number of people it routinely has to carry.

Option 3: Ground expensive older planes in favor of Trump's private jet

Justin Sullivan / Staff Getty Images

Yes, President-Elect Trump already has a private jet, a Boeing 757. It served him well enough during the 2016 campaign, but as a U.S. official told CNN, it's "nearly functionally impossible" for him to continue using it as the president. "No one tells the President he can't do something," the official said. "Instead, you lay out all the reasons it's functionally impossible."

Missing features on Trump Force One include missile defense systems, nuclear blast shielding, special communication systems for classified information, and the sheer size needed to carry the necessary staff. That's not to mention other unusual effects that result from the use of a private plane. During the 2016 campaign, the Secret Service detail charged with protecting Mr. Trump paid their way on his private plane using taxpayer money. Were he to continue on his private 757, such an arrangement would divert taxpayer money directly into the president's pocket every time he took a trip.

More importantly, this solution would leave the most glaring problems unfixed. Even if the aging VC-25s that serve as Air Force One today were grounded, they would still cost money to maintain in the event that their services were needed. After President Trump's tenure is over, be that in 2020 or 2024, the next president would wind up in the same situation we have now: old, expensive planes with no replacement in sight.

this solution would leave the most glaring problems unfixed.

Lastly, any attempt by President Trump to completely undo the Boeing deal could be thorny, considering a $170 million contract is already in place. However, the bulk of the cost of a new Air Force One is intended to be spread through the federal budget for years to come. Getting new planes to fly the president around is not an easy, cheap, or quick process. In fact, it's lengthy enough that President Trump may not benefit from it directly. It is, however, a problem that needs to be solved before complications can continue to compound. To simply ignore it because its price tag seems high would betray an egregious lack of foresight that could negatively affect U.S. presidents and taxpaying citizens for years to come.

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