Hello!

A friend of mine asked me a question which I am not able to answer because I normally only fly with Star Alliance members. Therefore I do not have a clue how to answer his question.

He has not joined any programm yet and he is flying on the 19th of April Stockholm-LHR-LAX with the cheapest not flexible economy class ticket on British Airways. The return flight is on the 1th of May.

He is a German based customer and always flying economy.
1. Which programm would you recommend is the best choice?
2. Are there any promotions he can use?
3. Is there a difference between the mileage credit within the onworld?

Any help is highly appreciated.
Many Thanks in advance! ^