Several United Auto Workers locals have filed grievances against Stellantis in a move that the union says could lead to a national strike against the carmaker.

UAW President Shawn Fain says Stellantis has backed off on plans to put a new product into the idled Belvedere Illinois plant. The union is also angry about recent cuts, including the elimination of a shift at Warren Truck.

Cornell University labor expert Art Wheaton says this reflects the more aggressive stance that Fain has taken as UAW President.

“I think he’s trying to make sure they’re protecting workers and fighting for workers as hard as they can. I think he’s demonstrated that he does not want to be, ‘Let’s all work together and be warm and fuzzy.’ I think he’s been much more adversarial in his approach, but it’s hard to argue with his success.”

While Stellantis has yet to comment on this new move, the company has in the past said they it needs manufacturing flexibility to remain competitive.