The bomb was planted on the plane in Canada, the attack was planned in Canada, the terrorists were Sikh Canadians, and the attack killed 268 Canadian citizens...
I see. I think our disagreement comes from the fact I don't think "Sikh Canadians" exist.
There are Sikhs in Canada, and they planted a bomb in Canada, but the location was incidental, in my opinion.
Unfortunately they possessed Canadian citizenship, making them Canada's problem. That's the unfortunate reality of having one of the world's most lax immigration systems and an embarrassingly low bar for citizenship.