If you have any passengers travelling on the Visa Waiver Program into Canada, they will have a few extra steps before being allowed to enter Canada. Only U.S. nationals are exempt from this requirement. Let's say, for example, you have a citizen of the United Kingdom spending time in the United States on the Visa Waiver Program, also known as a "green card." This person will have to obtain Canadian electronic Travel Authorization (eTA).
— James Albright
I've provided an overview of the process below, but your best source of information is from Canada: http://www.cic.gc.ca/english/visit/eta.asp.
3 — Documentation requirements
4 — What if you don't have an eTA?
For more information about the other aspects of this:
Who is impacted?
As of March 15, 2016, Canada will require Electronic Travel Authorization (eTA) for all visa-exempt foreign nationals entering the country by air. Effective this date, visa-exempt foreign nationals, other than U.S. citizens, must have an eTA prior to being processed by customs, immigration, and quarantine (CIQ) and entering Canada. In the past visa-exempt foreign nationals could travel to Canada without any specific advance travel authorization. This changes on March 15, 2016, with the introduction of the new eTA requirements for visa-exempt foreign nationals, regardless of their age. Only U.S. nationals are exempt from this requirement. U.S. permanent residents (Green Card holders) require eTAs to arrive in Canada by air. For example, if you’re a visa exempt national of the UK or Japan you’re now required to have an eTA to enter Canada, even though you did not require any advance travel authorization in the past. Note that new eTA requirements also apply to tech stops in Canada, even if passengers and crew do not leave the aircraft.
"Do I Need an eTA?" from Canada eTA website.
The screen capture here shows the results for a person travelling with a passport issued by France. You can check the countries you are interested in here: http://www.cic.gc.ca/english/visit/visas.asp.
How to obtain an eTA
- To complete the online form, you need:
- a valid passport from a visa-exempt country
- You cannot apply using a Refugee Travel Document, Emergency Travel Document, Organization of American States (OAS) Travel Document or a UN Laissez-Passer.
- If you are a lawful permanent resident of the U.S. and you do not have a passport, you can apply for an eTA with:
- a valid U.S. Refugee Travel Document (I-571)
- a valid Permit to Re-Enter the United States (I-327)
- a credit card
- Visa®, MasterCard®, American Express®, or
- a pre-paid Visa®, MasterCard® or American Express®,
- and a valid email address.
- You can only apply for one person at a time. For example, for a family of three people, you will need to complete and submit the form three times.
To apply for an eTA, see: http://www.cic.gc.ca/english/visit/eta-start.asp.
Source: Canada eTA website
According to contacts at Universal Weather & Aviation, Inc., once your eTA has been approved there’s no particular paperwork you need to carry it with you. An eTA is electronically linked to your passport. Note that you must always carry the passport you used to apply for the eTA with you.
What if you don't have an eTA?
According to contacts at Universal Weather & Aviation, Inc., if you arrive in Canada without a required eTA you may apply for one, via any computer or mobile device, prior to clearing the CIQ process. But, you will not be processed by CIQ until your eTA has been approved and confirmed.