Why can e-mileage be transferred but not used in combination with mileage that bears a different membership number?
The e-mileage originating with different members may not be combined. For example, Mr. Chen has 40,000 miles and Mrs. Chen has 20,000 miles. Mrs. Chen is traveling from Taipei to Los Angeles, and wants a free upgrade from Evergreen Deluxe Class to Business Class (a cost of 30,000 miles.) This could be possible if Mr. Chen transfers 30,000 of his miles to Mrs. Chen. He cannot transfer just 10,000 miles and use those miles plus Mrs. Chen’s 20,000 to secure the free upgrade.
