I’ve had several people contact me recently who are trying to track down long-lost flying buddies or people related to a particular era or area of aviation (for interviews, research, etc). Here are some general tips on how to do this online, as well as aviation-specific resources.
General:
1. Input the person’s name into Google (www.google.com) or some other search engine. It may sound obvious, but it’s always my first step and I usually try different things: putting quotation marks around the person’s name (“Pierre Berton” for example), to limit results, trying out nicknames, adding other keywords that might help (a place or thing you associate with them: Canada, Lancaster, etc).
2. If you know what city or province he/she lives in, you might be able to track a phone number and/or address through www.whitepages.ca (in Canada) or www.whitepages.com (in the US). www.411.ca and www.411.com are similar sites.
Aviation-Specific:
1. Email the Canadian Aviation Historical Society’s treasurer. She can check our database for a name, and if he/she is a member, can forward your contact info (because of privacy laws we can’t give you any of his/her contact info directly). 
2. Email the editor of the CAHS newsletter (cahs.newsletter@gmail.com) and ask to put a request for info in the upcoming edition. If your would-be-contact reads it, he/she can get in touch with you – or maybe someone else will know how to get a hold of him/her.
3. Email the editor of the CAHS Journal to put in a similar request.
3. If he/she used to work for Air Canada or one of its affiliates (Pacific Western Airlines, etc) then you could contact the editors of the Netletter through the AC Family Network https://www.acfamily.net for possible contact details (or a note in their newsletter).
4. If he/she may be a member of the Canadian Owners and Pilots Association (which has thousands of members), they might be able to help you out: https://www.copanational.org/
Happy hunting (and please add any of your tips in the comments below)!