Boeing on Monday offered its striking machinists a 30% raise over four years that it called the "best and final" contract they'll get after walking off the job earlier this month.

The new deal would boost the average annual pay for machinists from $75,608 to $111,155, with an initial 12% raise, followed by 6% during each of the next three years, Boeing said.

"After listening to our employees and their concerns, Boeing today presented our best and final offer," a company spokesperson said Monday, according to Reuters.

The proposal would also double the ratification bonus to $6,000, reinstate performance bonuses and increase the company's 401(k) matching contributions to 100%, according to a company flyer labeled "Best and Final Contract Offer."

Boeing gave about 33,000 members of the International Association of Machinists and Aerospace Workers a deadline of 11:59 p.m. Friday to accept the deal.

The union overwhelmingly rejected Boeing's previous offer by voting 94.6% against it, then voted 96% in favor of a Sept. 13 strike. That contract included a 25% raise, no performance bonuses and 401(k) match of 75%.

"Employees knew Boeing executives could do better, and this shows the workers were right all along," Brian Bryant, the union's international president, said in a statement, according to the Associated Press.

"The proposal will be analyzed to see if it's up to the task of helping workers gain adequate ground on prior sacrifices."

The union, which initially sought a 40% raise, had urged its members to approve the previous offer, calling it "the best contract we've negotiated in our history."

Boeing's chief operation officer, Stephanie Pope, had also called that offer "historic" and said workers wouldn't get a better deal.