Boeing Co. engineers on Wednesday became the planemaker's second union to demand the return of work farmed out to contractors — an issue that contributed to the strike started last weekend by 27,000 machinists.

The Society of Professional Engineering Employees in Aerospace, representing 21,000 Boeing workers in Washington state, Oregon, California and Utah, presented its first proposal to Boeing executives for a three-year contract to replace the one that expires Dec. 1, Executive Director Ray Goforth said.

The engineers may increase pressure on Boeing to take back work it gave suppliers to help control costs while developing and building planes like the new 787 Dreamliner. The machinists' strike shut down production at Chicago-based Boeing's Seattle-area manufacturing hub, where an increasing amount of the work is now the final assembly of parts built elsewhere by contractors.

"The fact the engineers are bringing up similar demands reinforces that this is a big issue for Boeing employees and strengthens the machinists' position," said Harley Shaiken, a labor-relations professor at the University of California at Berkeley. "We have a test of economic wills that could go on for quite some time."

The engineers' union is seeking raises, more vacation days, higher overtime rates, a restoration of early-retiree medical benefits and changes to the health-care plan and pension, Goforth said in an interview. The union also is "proposing limits to Boeing's use of contract labor," he said.

The proposal was presented to Boeing human-resources executives in Utah to show the union's opposition to Boeing's plan for separate negotiations with engineers there, who work on the company's missile program, Goforth said.

Boeing says it will need time to review the engineers' demands. "That could take a week or more, and then we'll provide a response," spokeswoman Karen Fincutter said in Seattle.

The engineers traditionally haven't walked out as often as members of the International Association of Machinists and Aerospace Workers. The machinists have stopped work over three of the last six contracts before this one, lasting from four to 10 weeks. SPEEA has only gone on strike twice: for one day in 1993 and for 40 days in 2000.

Engineers are watching the machinists picket and preparing for similar negotiations, Goforth said.

Machinists walked out when Boeing refused to go along with changes the union sought concerning the use of outside vendors. Boeing's offer of an 11 percent raise over three years also fell short of the 13 percent the IAM wanted, along with other measures. No new talks have been scheduled.