Unifor national president Jerry Dias said there was "no meaningful discussion" leading up to the 2 p.m. ET strike deadline on Monday.
Dias said morning meetings with Bombardier related to protocol in case of a dispute, and didn't focus on contract negotiations for the 900 employees.
He said Bombardier wants to make changes to pensions and benefits that are unacceptable to the employees and are similar to demands that caused a brief strike in 2011.
Bombardier spokesman Marc-Andre Lefebvre said the company is "deeply disappointed" that the employees are on strike.
"Throughout the entire process, Bombardier has been thoroughly committed to reaching an agreement that is both fair and reasonable," he said.
"We believe we've offered our Unifor employees a good contract proposal, one that obviously provides for well-paid jobs."
Lefebvre said the company is focused on minimizing the potential impact of the labour disruption on its customers.
Dias said Unifor is "prepared to stand its ground" in negotiating a new contract.
"We all need to work together to ensure that good jobs survive in this province," he said.
Dias said that the two sides were "stuck in the mud" over the weekend.
The company walked away from the table on Saturday, he said, and conversations the two sides subsequently had on Sunday produced nothing of significance.
"I came out here to find a settlement, but I can't reach a settlement if I'm just talking to myself," he said.
There are no new talks currently scheduled.
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