Boeing chief negotiator Doug Kight said the company was disappointed as talks broke off late Monday afternoon. The walkout is in its 38th day.
The president of the Machinists Union, Tom Buffenbarger, said by phone that the talks broke down over "the future" but declined to provide specifics.
Talks between the two parties resumed Sunday for the first time since 27,000 machinists went on strike Sept. 6 over issues that include job security, pay, retirement benefits and health care. The union also has concerns about provisions on outsourcing and subcontracting.
Boeing's Kight says the company wants its commercial jet production workers back at work but can't "sacrifice our ability to continuously improve productivity and our long-term competitiveness."