Boeing is the kind of manufacturer — one that exports billions of dollars of goods — that President Trump says he wants to protect and nurture.

But his tariffs could have the opposite effect on the company’s suppliers.

Mr. Trump has imposed a few tariffs so far, but he says more are coming in just a few weeks. That threat has unnerved the aerospace industry, of which Boeing is one of the largest companies. Duties on aluminum and steel, two of the most important raw materials used in aircraft, are expected to raise manufacturing costs. But the industry is far more concerned by tariffs that take effect on goods from Canada and Mexico next month, which could disrupt the highly integrated North American supply chain.

“These tariffs are particularly fraught for an industry like aerospace that has been duty-free for decades,” said Bruce Hirsch, a trade policy expert at Capitol Counsel, a lobbying firm in Washington, which has aerospace clients. “Parts are coming from everywhere.”

Aerospace experts say the industry is an example of U.S. manufacturing prowess. It offers well-paying jobs and has produced one of the largest trade surpluses of any industry for years. Aerospace is expected to export about $125 billion this year, according to IBISWorld, second only to oil and gas.

But the industry is operating under a cloud of uncertainty. Many companies have been able to avoid costly cross-border tariffs under a short-term reprieve for products covered by a North American trade agreement that Mr. Trump negotiated in his first term. But that deal expires in April.

In a letter to administration officials last week, groups representing airlines, plane repair stations, suppliers and manufacturers asked for an exception to the tariffs, arguing that it was needed to keep the industry competitive on the global market.

For Boeing, the tariffs would come at a difficult moment. The company spent the past year recovering from a crisis that started when a panel blew off a Boeing 737 Max jet during a flight in January 2024. There were no casualties, but the incident exposed shortcomings and prompted intense scrutiny from regulators. The company replaced its chief executive and began overhauling its operations.

After months of turmoil, including a nearly two-month strike, Boeing has steadily increased production of the Max, its best-selling jet, and other planes. But the tariffs could hurt the companies that supply it and other aerospace manufacturers. Aluminum makes up about three-fourths of the contents of the Max. Steel accounts for a much smaller but still substantial share.

The direct effects of the tariffs on Boeing will be limited, Brian West, the company’s chief financial officer, said at an investor conference on Wednesday. The company has a lot of inventory on hand and the company’s spending is already overwhelmingly concentrated in the United States. In addition, a rise in metal prices would amount to a less than 1 percent increase in the costs of making planes, he said.

But the tariffs could take a toll on companies further down the aerospace supply chain, which have struggled for years with material and labor shortages.

“What we do worry about is availability of parts because this is a broad complicated supply chain and people have different levels of exposure to it,” Mr. West said.

In all, the tariffs could raise costs for the aerospace industry by about $5 billion annually, said Kevin Michaels, a managing director of AeroDynamic Advisory, a consulting firm. A vast majority of that would come from the tariff on goods from Canada and Mexico. And the threat of a trade war would only compound the consequences.

“Not only are the country tariffs bigger, but countries can retaliate,” Mr. Michaels said. “And, boy, is Canada mad.”

Last month, Éric Martel, the president and chief executive of Bombardier, a major manufacturer of corporate jets based in Montreal, told investors that the company was suspending its financial projections for the year because the tariffs — and possible retaliatory tariffs — “could have an enormous impact” on the industry. Parts of Boeing’s 787 and 777 jets are built in Canada, which is also home to CAE, a leading manufacturer of flight simulators. Pratt & Whitney makes engines for helicopters and other aircraft in Quebec.

Mexico is also home to many suppliers, big and small. Collins Aerospace, Honeywell Aerospace and GE Aerospace design or produce components for commercial and business jets there.

If tariffs are imposed, analysts said, moving that production to the United States would be difficult, if not impossible.

“That’s going to take an awful long time to happen, if in fact it ever does,” Jerrold Lundquist, an industry consultant, said. “There’s fundamental economics as to why that supply chain is distributed in the first place. It’s usually labor costs, but also material availability and things like that.”

The industry operates on long time horizons — planes take years to design and months to make and are typically used for decades — so decisions to move operations are not made lightly. There aren’t enough skilled aerospace workers in the United States, and suppliers have struggled for years to hire enough workers.

In a report to Congress in November, a coalition representing the industry, workers and safety experts concluded that the “aerospace supply chain is vulnerable to labor shortages, obstacles in critical materials and the health of supporting infrastructure.”

Even the threat of an escalation in trade tensions is hurting aerospace manufacturers, industry experts said.

“The strategic decisions in a lot of cases are frozen as a result of this,” Mr. Michaels said.