Air Canada pilots went on strike today after failing to agree to a new contract with Canada's largest airline, setting the stage for hundreds of canceled flights and thousands of stranded passengers. Representatives of the carrier's 2,100 pilots and the company had been meeting almost nonstop since Thursday with the help of a government mediator. The pilots struck when their midnight deadline passed. They are seeking higher wages and better working conditions. Montreal-based Air Canada flies about 60,000 passengers on about 600 flights a day. The carrier has about 60% of the domestic market and flies to 42 U.S. cities, including Los Angeles.