Originally Posted by
threepoint
So a flight from purchased on AC.com, say, YVR-LHR-CPT with an AC plane on the first leg and a BA plane on the second, will only earn you Star points on the YVR-LHR leg?
It's a question that I'd pondered myself many times, particularly as AC.com frequently doesn't offer options using LH and never offers SAA onward from Heathrow.
It has nothing to do with whether you can book things on AC.com or not.
Earning miles has everything to do with being on a flight that earns miles according to the T&C published at aeroplan.com. If they wanted to give you miles for BA flights, that's their business.
AC.com only presents a subset of flights that AC is willing and able to sell you. If you called them on the phone I'm sure they would be happy to sell you a ticket that takes you to LHR and onward to CPT on SA.