At least 1,800 workers will leave Boeing through voluntary buyouts as the company moves ahead with job cuts announced in December.

The International Association of Machinists, which represents factory workers in Washington State, said 1,500 of its members will take buyouts. The Society of Professional Engineering Employees in Aerospace, which represents engineers and aircraft inspectors, had 300 members take the package.

Nonunion workers at Boeing were also offered buyouts, but the company won't say how many accepted. Boeing is offering a week of pay for every year of service, up to 26 weeks, plus six months of medical insurance.

The company says it will also use attrition and layoffs to reduce head count by a yet to be determined number.

As of last month, Boeing had 75,000 workers, or about half its total work force, in its commercial aircraft unit, where the buyout offers were made. The company had already cut head count in the commercial aircraft unit 9% in the past year.

Related: How Boeing got on Trump's good side

Boeing (BA) has been cutting staff as it adjusts to weaker sales of some of its jets, especially older widebody models. The company notified staff of plans for additional job cuts in December, and the unions are bracing for additional layoffs.

"We know there will be more cuts this year," said Bill Dugovich, spokesman for the engineer and aircraft inspector union. "We're told it'll be in line with last year, at least."

Related: Boeing warns more job cuts coming in 2017

Just last month, President Trump visited a nonunion Boeing plant in South Carolina to promote American jobs.

"Already, American industry is roaring back," he said at a ceremony unveiling Boeing's newest jet. "Jobs is one of the primary reasons I am standing here today as your president, and I will never, ever disappoint you, believe me."

But Boeing has also cut jobs at the South Carolina plant, which opened in 2011.