I bought a ticket for my wife coming from the Philippines to Canada to the US there was no mention of any kind of visa form required for entrance into Canada. She was denied to check in to the flight because of not having her Electronic Travel authorization. I was woken at 3 am by my panicking wife and had to fill out this form at the last minute which of course didn't get approved in time and she was denied onto the flight. So for future travelers you might want to give them a heads up.