I wonder if any of the above repliers actually booked any companion award tickets or not?!?!

Here's some information from my experience;

1. You don't have book "FULL FARE" Biz or first to qualify for companion eligibility. Even "I" fare will do.
2. All you have to have is a reserved reservation to start the process.
3. Once you've booked your companion seat, you'll have 1 week to pay for the primary ticket and issue the award.
4. Nobody mentioned miles... you do need Asia miles you know? Just not the full shebang. Roughly half. For instance, HKG-LHR-HKG in biz requires 75,000 miles
(instead of the normal 140,000)
5. You pay airport tax - same amount as you would for the primary ticket.

Using Amex Platinum, you don't need miles, just pay full fare. However, flights have to originate in the US.

Hope this helps.

KK