Originally Posted by anabolism

Crediting to some programs can earn widely different amounts depending on the marketing carrier. For example, when crediting to AA, AA, BA, and IB flight numbers earn by fare (prorated by flight distance), which on an RTW is typically miniscule. An MH or QF flight number earns barely more than the flight distance, while an AY or JL flight number earns a nice multiplier of flight distance. Different starting points may enable different codeshare flights.