Technically, you can't do that. If you miss a leg of your flight, they will automatically cancel your returning flight. I flew from YYZ to SNA through SFO and at the last minute decided to stop at SFO and visit SF for a week. I called to ask if I can end the flight at SFO but still use the returning flight from SNA to YYZ but AC said that's not possible. I got the manager on the phone but no avail.

So I decided to fly all the way to SNA and fly back to SFO. I purchased a SouthWest flight from SNA to SFO. That would've been an ugly route. YYZ->SFO->SNA->SFO. I went to the airport all ready to endure the flight. I asked noce more at checkin if he could end the flight at SFO for me and he said no problem and I was on my way to SFO. As soon as I got through the security, I called up southwest and got my refund. Southwest is great for their return policies. And the return flight was still valid.

So our routing ended up being YYZ->SFO and SNA->DEN->YYZ for return. So just ask at the checkin nicely and they may honour your request. Don't bother calling AC because I tried for hours with many CSR's and managers to no avail. Good luck!

By the way, they took away my screwdriver on that flight. I thought it'd be ok because it has a dull point. I flew with it many times prior. And I don't know how they expect you to check it in if I'm already checked in, passed the customs, etc. No big deal.