I have recently flown on SilkAir from Singapore to Phuket and could not justify paying more than five times more (S$1,300) for a 90-minute flight - the same flight in Economy costs approximately S$240. With that being said, the MI Upgrade is something that people do not talk about often. It is basically a bidding system that allows you to make an offer to SilkAir to upgrade your flight from Economy to Business - if the bid is unsuccessful, you do not pay anything at all and if it is, you pay the amount that you have offered.