Employers are not entitled to unpaid work.
"Despite meeting multiple times each month since September, the union says the main sticking point with the airline is the approximately 35 hours of unpaid work it says flight attendants are required to perform each month. According to CUPE, many flight attendants in Canada are generally not paid their regular hourly wages during boarding, pre-flight safety checks and other delays."
https://www.ctvnews.ca/business/article/westjet-flight-attendants-escalate-contract-dispute/