The Canada Industrial Relations Board had declared the strike illegal earlier on Monday and ordered the striking flight attendants back on the job. But the union said it will defy this second return to work order, after an earlier one had been ignored. The earlier one also ordered the union to submit to arbitration.

If you've been following the Air Canada strike throughout its twists and turns, you've likely heard the term "ground pay," or noticed flight attendants holding signs decrying unpaid labour. But what is that unpaid work?

While Air Canada says it would not negotiate with the union until flight attendants return to work, CUPE says the two sides were in discussions Monday night with a mediator.