But I notice for Long haul flight, the miles required is more than 15% miles discount but the extra miles cost is about $0.03miles
For short haul flight, the miles required is exactly 15% miles discount but the extra miles cost is higher, about $0.06/miles
Eg: Long haul
SIN-BCL needs 59500miles but now need 76000miles, which is about 28% more miles but the cash payment is difference of $423.80 ($0.03/mile)
Eg: short haul
SIN-MLE needs 31450miles but now need 37000miles, which is exactly 15% more miles but the cash payment is difference of $306 ($0.06/miles)