Note that this works well when redeeming miles over the phone. They take some (very basic) "security" questions and they deduct miles from the other member's account.

However, at the airport this doesn't work. If you want to redeem an award using someone else's miles (you are on their redemption list), they will not do this unless the member whose miles you are redeeming is there in person, they want a signature.

Not sure why the double standard, but that's the way it is. I know because I tried to redeem an upgrade award using my son's miles earlier this month at the CX lounge in HK (I am on his redemption list), but they wouldn't let me because my son wasn't travelling with me and couldn't personally sign the request.