We've always heard great things about Singapore Airlines. For more details take a look at the site SeatGuru, which offers information about SIngapore Airlines bassinets (baby carriers), plus if you know the type of aircraft you will be travelling on you can check what baby friendly facilities will be available.

Also see SIngapore Airlines own site for details of flights with infants: Special Needs -- Singapore Airlines. You can contact them direct on their flight enquiries line: 0844 800 2380

Also take a look at the following posts for advice from parents on long haul flights with infants:
flying to Oz from UK with 6 month old baby please help!!!
Long Journey down under
Travel tips for mum flying with 17month year old (very active!) boy on her own!