Analysts say a strike could cost Boeing about $100 million per day in deferred revenue. In 2005, Boeing was unable to deliver more than two dozen airplanes as scheduled because of the strike that year.
Boeing's union machinists have walked off the job six times since the labor group was formed in 1935.
"We're supposed to be a world class company, but they don't want to give us a world class contract," Robert Eagleson, a union steward at Boeing's Renton plant, said Friday.
Boeing's latest offer followed a counterproposal from the union asking for more money and stronger language about job security.
Besides the proposed wage hikes, the offer included pension increases and a 3% cost-of-living adjustment. The added pay and benefits would total an average $34,000 over the life of the three-year contract, according to the company.
The average Boeing machinist earns $27 an hour, or about $56,000 a year, before overtime and incentives.
Scott Hamilton, an analyst with Leeham Cos., said earlier that such bargaining usually continued until seconds before the deadline, but that Boeing had thrown a "Hail Mary pass" five days ahead of time in hopes of appealing directly to union members.
"Boeing is rolling the dice on this, there's no question about that," he said.
From a financial standpoint, Hamilton said, the offer appeared to be "pretty good" for a labor force that hasn't had a wage increase in its past two contracts.
But he believes the union was looking for more — perhaps 13% rather than 11% in wage increases, he said.
The effect of a possible strike would depend on its duration, particularly for Boeing's 737 and 777 production lines, which are running at capacity, with 31 737s and seven 777s produced monthly, Hamilton said.
The union currently represents 25,000 Boeing employees in the Seattle area, around 1,500 in Portland and 750 in Wichita.
Boeing's commercial airplane manufacturing operation, based in the Seattle area, has led a resurgence by the company over the past two years amid heavy orders for the much-awaited and increasingly delayed 787.
But Boeing faces billions of dollars in anticipated additional costs and penalties, with three delays in the 787's delivery schedule that leave it more than a year behind the original schedule.
Airlines, meanwhile, have been struggling with rising fuel costs. Several carriers have posted big losses in recent months and some have been forced to postpone aircraft deliveries.
Shares of Boeing fell 78 cents, or 1.2%, to close Friday at $65.56.