The government creates the Secure Air Travel Act list based on a dual threshold of identifying individuals who are suspected of posing a threat to airlines but also individuals who are suspected of travelling abroad to participate in terrorist activities. That is not to say that airlines don't have their own lists, but they're not terrorism-related. Airlines will have their own list based on people who've had rage fits on airlines and things like that.
There's quite a complex process in place when somebody is flagged at registration. They may be on the SATA list. There's a whole process going back to the government, to Transport Canada, and to Public Safety to vet whether or not that person is a close name match or an actual person on the list.