On my very first flight on CX I used credit card Asia miles to get a free ticket and politely asked the check-in agent if i could get an upgrade since it seemed like there was no one on the flight. Anyway she smiled and politely said, 'no, we reserve these seats for our gold card members or above, but you can however use your miles to upgrade.. let me check how many miles you have.. hm... 3000..no you can't.." haha.. i felt funny but didn't loose anything in asking.^