The currency displayed is dependent upon the region selected on the aa.com website

If set to Canada, it shows Canadian Dollars ( CAD ) , if set to Australia it shows Australian Dollars (AUD) and if set to USA, it just shows $ - if just showing the '$' currency symbol rather than a currency code, then you are set to United States for the site and the price is in USD

If you want to pay in Canadian Dollars, change the site to Canada and it will price in CAD