The easiest status is on QF if you fly in F/J, and on AA for discount economy. Several of the OW airlines (QF, BA) greatly differentiate in status earning between premium and discounted fares (an order of magnitude), while the mileage-based status earning airlines only have a factor of 1.5 instead of 10x. The other wrinkle in OW is that a mile on one airline is often worth 2 or 3 miles on another airline, it all depends on your earn and burn patterns. If you are looking to optimize things, you got to do the math for your own situation (and it does come down to fare codes). If in doubt, AA is the best. OW doesn't have any airline as desperate as BMI, so no such sweet deal in OW as in Star.