Updated from 7:30 a.m. EST



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employees returned to work on Monday after the

Society of Professional Engineering Employees in Aerospace

ratified a labor contract that put an end to one of the largest white-collar strikes in history.

The 40-day strike of some 15,000 SPEEA members threatened to cause a potentially disastrous bottleneck of aircraft deliveries and a reduction of flights for summer travelers. The professional engineering bargaining team approved the three-year contract by 71.5% late Sunday, while 70.7% of SPEEA members voting in the technical bargaining unit voted for the contract.

Boeing shares were trading down 15/16, or 2.5% at 37 1/16 around midday Monday.

"Boeing is delighted that SPEEA members ratified the tentative settlement, and we are looking forward to their return to work," Phil Condit, Boeing's chairman and chief executive, said in a statement.

SPEEA represents approximately 20,300 engineering and technical employees in the Puget Sound, Spokane, and Portland, Ore.

In its agreement with the union, Boeing backed down its demand for co-payments on employees' health care insurance. The company also added a $2,500 bonus, although $1,500 of that bonus is tied to Boeing's goal of delivering 491 commercial jets in 2000.