Wichita ? The professional and technical workers at Boeing Co.’s Wichita plant will vote Wednesday on a contract offer, their third during the current negotiations. This time, a strike could hang on the outcome.

The Society of Professional Engineering Employees in Aerospace — which narrowly survived a decertification vote in February — has made no recommendations on how members should vote, saying only that it includes “minor improvements” from earlier offers.

“It is their contract. It is their decision. It is up to them to make the choice,” said union spokesman Bill Dugovich. “That comes with the understanding that if this contract is rejected, there will be a strike. So when the stakes are that high, it really is a member decision.”

Boeing told its managers in a memo the extended four-year proposal gives the company the ability to “balance employees’ desires for stability and predictability with Boeing’s need for the flexibility to remain competitive.”

Boeing spokesman Dick Ziegler said the company was “fairly certain” it could continue operations at the Wichita plant in the event of a strike by its second-largest union, which represents 3,400 employees.

“But we would rather not do it without our (union) employees. We would prefer they be included,” Ziegler said. “If they take a look at this offer, I think they are going to find all the elements they asked for, in some shape or form, are here. And in that regard, I am optimistic.”

In May, more than 70 percent of members of the union’s Wichita Technical and Professional Union voted against a contract offer. At the same time, nearly 75 percent also voted to authorize a strike, in hopes it would give their union more negotiating muscle.

In the first vote in March, workers rejected the company’s offer by a 3-to-1 margin.

B.J. Moore, the union’s contract administrator, said the latest contract’s wage and benefit package still falls short of what the union wanted. But union leaders also felt it was their obligation to let workers — not the negotiation team or the union staff — decide whether they wanted to walk out over it.

The latest offer includes wage increases of 3.5 percent the first year, 3 percent the second and third year and a “market percentage” in the fourth year. A $1,800 lump sum is payable if the contract is approved.

The offer caps for the first three years of the contract the monthly health care premiums at $89 for an employee, $178 for an employee and spouse or children, and $267 for a family enrolled in its traditional plan. Boeing also has a no-cost health plan.

The offer also includes a side agreement relating to the possible sale of part of the Wichita facility. In it Boeing agrees to share information regarding the terms and conditions of employment so employees could make their own “personal employment decisions” in the event of a sale.