I'm trying to book a flight to SA from YVR and would like to fly AC to LHR then SA to JNB or CPT. When I search on AC.com I only get flights on BA, or on Swiss via Zurich. I can find the flights I want on expedia or orbitz.

Is there some reason the SA flights don't show up on AC.com? Wouldn't it make more sense for them to sell the *A partner preferentially rather than BA?