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?

Striking Air Canada flight attendants vowed Monday to defy another back-to-work order from the country's labor tribunal, but resumed talks seeking to end a walkout that has cancelled travel for half a million people worldwide.

Air Canada and the union representing 10,000 flight attendants resumed talks late Monday for the first time since the strike began over the weekend. The strike is affecting about 130,000 travelers a day at the peak of the summer travel season.