Beginning March 15, 2016, visa-exempt foreign nationals will require an Electronic Travel Authorization (eTA) to fly to Canada. U.S. citizens are exempt from the eTA requirement.
If your study or work permit was issued on or before July 31, 2015, you will need to apply for an eTA if you wish to enter or return to Canada by air on or after March 15, 2016.
If you received your study or work permit on or after August 1, 2015, you were automatically issued an eTA with your study or work permit.
For more information, and to apply for an eTA, please visit Canada.ca/eTA.