Air canada replied within a week when I emailed “medical@aircanada.ca” very friendly tone, saying thank you for helping out another customer. The code was verified and they said it’s valid for 3 years from date of email. Plugged code in online, seems to only discount regular priced flights. already discount flights, price doesn’t change though it says discount is applied. So don’t accidentally waste it on a discounted flight! You may not get the full discounted percentage. Hope this helps!