Unifor, the union that represents the 4,000 employees, says it was officially notified Thursday of the move, which will eventually start the clock ticking to a possible strike or lockout no earlier than May 11.
Leslie Dias, the union's lead negotiator, says talks will continue to try an reach an agreement.
"We're making some progress on issues. There's no particular issue that is causing a dispute at this point in time," she said in an interview Thursday.
The union last week suspended talks for a few days after Air Canada released changes to shift-trading rules.
Air Canada agreed some progress has been made, but said the assistance of a conciliator would be helpful to "make progress towards a comprehensive agreement."