Apologies if this question has already been asked before - I did a search and couldn't find anything.

A friend of mine is going on a One World round the world trip (LHR-HKG-SIN-DPS-DAR-PER-MEL-AKL-SCL-EZE-GGU-LHR) in Economy and asked me for advise on which mileage program to join. His primary objective would be to make as many bonus miles as possible, he is not interested in obtaining status (though it would certainly be a nice additional benefit).

I did a bit of research and think American Airlines might be a good program for this purpose - is this true, or did I miss out on something?