Precision Castparts welders won a victory before a federal appeals court this week, potentially clearing the way for them to organize — more than three years after the Oregon workers voted to unionize.

The Portland company, a key Boeing supplier, refused to bargain with the 100 welders and challenged their organizing effort, arguing that their work was too closely integrated with the rest of the company to constitute a distinct union.

The National Labor Relations Board disagreed, finding that Precision Castparts had committed an unfair labor practice. Precision Castparts challenged that decision in court, losing its case Tuesday before the U.S. Court of Appeals in Washington, D.C.

The union, the International Association of Machinists and Aerospace Workers, said Thursday that with the appeals court’s ruling in hand it will send a demand letter to the company and hopes to begin negotiating a contract.

“It’s been a long battle for these guys,” said Billy Anderson, an organizer for the national union. “Hopefully we can move forward and they can respect the wishes of the welders out there.”

Precision Castparts makes heavy metal components for jet aircraft and other industrial products. It was among Oregon’s biggest companies when it sold to Berkshire Hathaway, Warren Buffett’s investment firm, for $37 billion in 2016.

Precision Castparts struggled last year amid the downturn in global aviation and because of Boeing’s setbacks with its 737 MAX plane. The company laid off 40% of its global workforce.

Its revenue had been stagnant for several years, though, and earlier this month Buffett admitted that he’d overpaid by $10 billion for the Portland company.

Precision Castparts didn’t immediately respond to a message Thursday seeking comment on this week’s court ruling, so it’s not clear whether the company will seek to appeal to the Supreme Court. Anderson said the union is hopeful it will not, and that negotiations can now begin.

“We typically haven’t had this kind of relationship with them, especially with Warren Buffett promoting himself as pro labor,” he said. “The ball’s in their court. It’s my hope they wouldn’t do something like that.”