You are correct on Boeing being very conservative before launching the 747ADV. They want to make sure that they have commitments for atleast 50 aircraft before they launch. Here is an interesting thing that I heard three weeks ago. Boeing is pressuring Virgin to accept the 747ADV instead of the 744. However Richard Branson told Boeing he is happy with the 744 and would gladly order more if they reduced the price. Boeing, sensing a loss in a potential 747ADV order here has refused to accede to his demands. Thus the stand off.