So you completely discount the fact that over 70 percent of all 747s were bought for their RANGE and not their size? So the 30 percent of 747s that were bought for their size are available for trade up, but what killed the 747 on the north atlantic was not a bigger aircraft. It was a smaller one that could now fly that range efficiently.
And as the 777/340s grew in range they replaced more and more 747s even though the 340's seat mile costs were higher if you filled both aircraft. The problem is that airlines most markets couldn't support a 747 so the smaller 340s 767s and 777 were better for the job since they could fly that distance profitably now.
Amazing how easily you discount the last 15 years of history or so...
CHeers
Wino