Maximum permitted mileage or MPM is mysterious to me. I called the Aeroplan Contact Centre asking about an itinerary I'm planning SFO-BKK with stopovers.

They said the MPM for SFO-BKK was 9506 miles (each way) so plus the 5% they allow comes to 19962, if my math is right.

But it seems others have booked routes exceeding this mileage. So this question:

Is MPM a fixed number that Aeroplan uses for all awards, or does it depend on what airline you fly, or just what any Star Alliance member might publish? In other words, is MPM the same for all Star Alliance members?

Thanks