MH (Malaysia Airlines)
one of the Gulf-area airlines (no, SV (Saudi Arabian Airlnies) doesn't count -- EK, QR or EY, though I know it will never happen)

But continuing recent trends I actually predict the next member will be JS (Air Koryo). And also that FTers will complain that JS gives 0% mileage for many discounted Y fares and only 50% mileage for many others, and that their award redemption calendar is broken...