Originally Posted by
Collierkr
my advice when traveling to another country is to always check with that country. Don’t rely on airlines and quite frankly it is not their job to educate the traveler.
This is good advice, but United does also confirm you need one. From a dummy LHR-YYZ-EWR booking through UA with the first leg on AC. I guess UA could say "to or through" the country, but the eTA is mentioned on the booking.
It's especially odd that they confirm you need the ESTA to fly to or through the US. But that's a UA issue.
