Thousands of Qantas Airways passengers face flight delays and cancellations because of a strike by its engineers.

Australia's flagship airline says 40 domestic flights will be cancelled. Another 27 domestic and 11 international flights will be delayed or rescheduled.

The engineers' union planned to walk off the job for four hours Monday as it fights the airline over pay and work conditions.

The airline estimates the strike will affect more than 11,000 passengers.