Air Canada flight attendants want to make gains on unpaid work that go beyond recent advances secured by their U.S. counterparts, a union leader said on Wednesday, in a fresh test of the way airlines compensate cabin crews.

Canada is battling more than 700 active wildfires across the country, roughly two-thirds of which are burning out of control, according to the Canadian Interagency Forest Fire Center (CIFFC). Smoke billowing from the blazes has blanketed central Canada and the northern U.S., prompting widespread air quality alerts.

Air quality alerts remain in effect from Minnesota to the Northeast due to smoke from hundreds of wildfires in Canada. In the West, wildfires in California continue to rage.