Union leaders have circulated a letter "asking members to ignore the call for a wildcat strike," said Ray Goforth, executive director of the Society of Professional Engineering Employees in Aerospace (SPEEA) said in an email to Reuters. "We've also posted such messages on our Facebook page."
The response comes after union members apparently sent emails from fake accounts calling for a one-day walkout on Wednesday.
Boeing officials didn't immediately respond to a request for comment.
Talks between Boeing and SPEEA broke off last week after Boeing called for a federal mediator, saying the sides remained far apart even though they have been negotiating since April on contracts that expired in October. A 60-day extension expired November 25, opening the door to a strike.
On Friday, the two sides tentatively agreed to resume talks on Tuesday with a mediator present, provided they could agree on a venue and the choice of mediator.
The union has balked at a Boeing contract that it says would cut the growth rate of compensation of professional and technical employees. Boeing says its latest offer is much improved over its initial proposal and reflects a tough competitive environment.
The dispute comes as Boeing is speeding up jet production from 52 a month, worth about $8 billion at list prices, to about 60 a month by the end of next year. A walkout by the union could stop production and could cost the company about $400 million a day at current production rates and prices.
"No question there would be steep costs" to Boeing from a longer, union-sanctioned strike, said Richard Aboulafia, an aerospace analyst at The Teal Group in Virginia. A delay in production, particularly of Boeing's 787 Dreamliner, would help jet maker Airbus catch up on competing jets.
A union-sanctioned strike, which might last only a few weeks, would have minimal effect on planes still in development, such as the 737 MAX, he said.
The last strike by SPEEA, in February of 2000, lasted 40 days and came after a mediator failed to resolve differences.
Goforth said those calling for a strike were frustrated with Boeing "for trying to impose a terrible offer" and impatient with the plane maker's negotiations tactics.
"They wanted to inflict some economic harm and signal to the customers and investment community that Boeing is about to provoke a serious strike."
The union said the one-day strike is not sanctioned by SPEEA and is not legally protected.
The union also said it had no plans to strike before the holidays, because Boeing closes its factories for the week between Christmas and the New Year holiday.
"We don't know whether such an action will happen December 5," Goforth said, because the union doesn't know how widespread the planning is nor "how many people will heed SPEEA's call to not participate in this action."
Shares of Boeing edged down 3 cents to $74.09 in Friday trading.
(Reporting by Alwyn Scott; Editing by Doina Chiacu)
By Alwyn Scott