On Tuesday, Malaysian Prime Minister Mahathir Mohamad told reporters he's studying whether to sell, shut down or refinance Malaysia Airlines Bhd., the troubled national carrier. A decision needs to be made soon. In 2018, the perpetually money-losing airline accounted for about half of the US$1.5 billion in losses suffered by its parent, Khazanah Nasional Bhd., Malaysia's sovereign wealth fund.On purely economic terms, Mahathir’s decision should be easy.