WestJet passengers could face widespread flight cancellations over the August long weekend after the airline's flight attendants issued a 72-hour strike notice, raising the possibility of travel disruption across Canada.

The union representing around 4,400 WestJet Mainline flight attendants, CUPE 8125, voted in favour of strike action.

Under Canadian labour law, a work stoppage could begin as early as 2 August.

WestJet has also issued a 72-hour lockout notice, although negotiations between the airline and the union are continuing.

The union said the two sides remain "still too far apart," despite months of bargaining over wages, scheduling, work-life balance and other workplace issues.

According to reports, WestJet is preparing to operate a reduced schedule and may begin cancelling flights before any strike action starts.

The airline said it will "take all necessary actions to manage the potential impacts as much as possible."

Passengers travelling between 30 July and 4 August can take advantage of flexible change or cancellation options, provided changes are made more than two hours before departure.

Air Canada said it is "prepared to assist" affected passengers where seats are available, but warned capacity is limited because the August long weekend is one of the busiest travel periods of the year.

Under Canada's Air Passenger Protection Regulations, compensation during labour disruptions is limited, although some passengers may qualify for payments if rebooked flights are significantly delayed.