It is important to remember that visa-exempt foreign nationals flying to Canada will need an Electronic Travel Authorization (eTA). This requirement does not apply to U.S. citizens and travelers with a valid visa.
Applying for an eTA is quick, easy and can be done as of now. In most cases, the authorization will be received within a few minutes.
All of the necessary information can be found on the Government of Canada’s website: http://www.cic.gc.ca/english/visit/index.asp