And don't forget anti-trust issues... unless airlines hold significant cross holdings (like OS/LH/CL/EW/LX/LO or BD/SK/JK/KF/BN/WF) they are not allowed to share revenue, load factor and other pax demographics. Marketing/code share agreements already push the limits of what is allowed. LH/UA, AA/BA and NW/KL had quite a battle till they were allowed what they currently do.