The UAW reported that 8,700 workers walked out of the truck plant in Kentucky in protest to Ford’s refusal to go forward in contract negotiations.
It is a significant increase in the company’s strike against Ford, General Motors, and Stellantis, which began last month.
The UAW is urging automakers to increase salaries and make other concessions in new labor agreements.
It is the first strike in the union’s 88-year history to target the Detroit Three automakers at the same time, which employ more than 140,000 UAW members collectively.
The UAW represents almost 400,000 active workers in a variety of industries, including hospitals and universities.
Workers at US automakers begin a historic strike.
The car workers’ strike is entering its third week.
With Wednesday’s walkout, which halted manufacturing of lucrative pickup vehicles, about one-fifth of auto workers have now stopped working.
Ford termed the latest UAW effort “grossly irresponsible” in a statement.
Ford’s truck facility in Kentucky generates $25 billion (£20 billion) in annual income, accounting for one-sixth of the company’s global automobile revenue.
The latest walkout serves as a warning to General Motors and Stellantis, which are now negotiating with the UAW.
It also comes at a time of widespread labor upheaval, casting a pall over an industry that accounts for 3% of the national economy.
Two weeks ago, US President Joe Biden became the first sitting US president to visit a picket line in support of striking autoworkers in Michigan, saying the workers “deserve” raises and other concessions.
