Boeing did show those mockups. But I have heard that Boeing also started building 2 metal airframes which were supposed to fly when complete. How far did those get?
Absolutely nowhere. All that money spent and no progress on solving the many severe problems of unre-heated supersonic flight. Of the list of aeroplanes that did solve that one, I believe the list starts and ends with Concorde. It took Concorde 6 years of development flying to achieve service entry. That intake geometry alone is a nightmare. Technically successful, commercially a failure, it was a plane out of its time. I believe like the Apollo moon landings, it was a science out of its time- hugely successful, but mankind just couldn't take it. They shouldn't have worked, but they did, through sweat and faith. But ultimately they both failed because they were just too big jumps in technology. The 2707 cost
more than the whole Concorde program, and produced nothing. It would have failed hugely, as they knew. They got absolutely nowhere building any parts for it, so we must understand it wasn't waiting to come on the scene!
And Concorde came out of friendly Anglo-French co-operation! How? Didn't they do well?