Originally Posted by Ew/oQ

Did this many many times for my late wife. However, this was in 2013 so things may have changed. My experience…
-Get "number" from Air Canada medical desk first. Issued after documents submittal and approval. (I forget the term used for the number). Do this before booking any tickets.
-Book the AE ticket and immediately YOU phone the medical desk. (Never more than a minute or two to answer). Using the “number" book the companion ticket.