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

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

Trump has imposed a few tariffs so far, but he says more are coming in April.

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 Hirsh, 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 Trump negotiated in his first term.

But that deal expires in April.

In a letter to administration officials this month, 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, prompting intense scrutiny from regulators.

The direct effects of the tariffs on Boeing will be limited, Brian West, the company’s chief financial officer, said last week at an investor conference.

Aluminum makes up about three-fourths of the contents of the Max. Steel accounts for a much smaller but still substantial share.

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% 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,” 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.