I doubt about supersonic jets ever becoming as fuel-efficient as the subsonic ones of the same generation. Of course, in a world that had no 1973 and 79 oil shocks, it may be not enough of an issue to cripple the SST as a whole, but it still looks like a dead end alley to me. Besides, TTL has telecommunication technologies developing well ahead of OTL, so there's just as little need to keep it as some kind of transportation for the executives.
Yes, I think that's fair enough. To a certain extent the 'fuel efficiency' argument is kind of a cover (although the savings are real enough) for having a Commonwealth company producing 'the best and fastest' plane in the world.
Perhaps Concord still has a French 'e' on the end because it was a joint project with Canada to bring the Commonwealth together across the ocean?
Very good point - I should probably reinstate the 'e'.
You mentioned Cunard and White Star. How do you imagine the Commonwealth's airlines to have developed? Is there a separate BOAC, BEA, British Airways and Imperial Airways? And is Freddie Laker still in business?!
BEA and BOAC don't exist, as such. BEA in particular doesn't exist because the companies that merged to form it OTL - notably De Havilland and Hawker Siddeley - are still thriving companies in their own way. In particular, the disasters that so damaged the Comet OTL happen instead to the Boeing, meaning that De Havilland has become one of the largest aircraft manufacturers in the world. Hawker Siddeley is smaller than that but still a thriving Commonwealth-wide manufacturer.
As for the airlines, there is a pretty competitive Commonwealth-wide market and improvements in jet technology mean that most of the important ones now offer global coverage (to differing degrees) even if they started out as regional ones. I had imagined that Qantas, Pacific Western, Ceylon Air and Air Africa (TTL's version of Kenya Airways) would be pretty significant. Imperial Airways is still around and is basically the flag carrier of Hong Kong and the East Indies.
British Airways exists and is considered to be the UK's flag carrier, even if it was never nationalised. Instead, the SWF bought shares in 1948 and remains a significant shareholder to this day.
i don't really foresee Freddie Laker still being in business unless the various changes in TTL make him a completely different person. That being said, there are no-frills airlines (EasyJet, in particular, comes to mind) and most mainstream (for want of a better word) airlines offer a low-cost service. In practice, there's less of a demand for these than you might think, even in large countries like Canada and Australia, due to a couple of factors: firstly, improvements in high-speed (and relatively green) railways mean there's less need for them; secondly, improved telecommunication means there's less need for businessmen and executives to fly around on whistle-stop tours, meaning that most people might only fly to get to and from their holidays.