score:19
If your itinerary is one ticket with one record locator number, then the carrier will examine your paperwork at your first check-in to ascertain if you are admissible into your final destination in Canada. If they determine you are inadmissible (here, because of missing paperwork), the airline will not allow you to board the first flight.
Every airline has Terms and Conditions that place responsibility for having the appropriate paperwork and documents on the traveler. If they deny boarding, the airline will neither offer nor provide any compensation or relief to you.
Thus, you must have the negative PCR test results available to you at check-in in Belgium.
Upvote:11
Your credentials for entering the destination country will be verified when you are checking in and not when you board the plane. If you don't have all the paperwork ready when you start the trip in Belgium, you must really expect that the airline will not let you fly.
It is of course in possible that you can explain the situation and ask them for an exception, but at least I would not at all rely on the airline to do so.