25% salary increases in depth four years old promises the Boeing to its staff in an effort to avoid a strike that could potentially shut down production lines in the US.

Union leaders representing more than 30,000 workers urged workers to support the proposal, calling it the best contract they had ever negotiated.

If approved, the deal would be a major achievement for Boeing’s new chief executive, Kelly Ortberg, who is under pressure to fix the company’s quality and reputation issues.

Boeing workers in the Seattle and Portland area are set to vote on the deal Thursday. However, the scenario of workers going on strike has not been ruled out. That could happen if two-thirds of union members back it in a separate vote.

In a video message to Boeing employees, the company’s CEO, Stephanie Pope, described the proposal as “historic offer”.

If ratified by union members, it would be the first full labor agreement between the company and unions in 16 years.

“We can honestly say that this proposal is the best contract we have negotiated in our history,” the International Union of Mechanical and Aerospace Engineers (IAM) said in a statement.

In addition to the pay increase, the deal offers workers improved health care and retirement benefits and a commitment by Boeing to build its next commercial airplane in the Seattle area. It also gives union members more say in matters of safety and quality.

“Financially, the company is in a difficult position due to many self-inflicted errors. It’s the IAM members who will get this company back on track,” negotiators said, referring to the crises Boeing has faced in recent years.

Mr. Ortberg, an aerospace industry veteran and engineer, took over as Boeing’s new chief executive last month.

His appointment came as the company reported deeper financial losses and continued to struggle to repair its reputation after recent incidents on its planes during flights and two fatal crashes five years ago.