[trhway]

>2. The engines would be far more fuel efficient

not really. In supersonic regime Concorde engines were pretty good, and you'd not beat them today by much.

Concorde was using afterburners to accelerate to supersonic and this is where it burned a lot of fuel. Designing engines which would give you good thrust at subsonic speeds without afterburners and would still perform well in supersonic is still much unsolved. Just look at the best military engines today - they all under Mach 2 and can't give even 3000 miles range.

And without increasing efficiency we can't really get much beyond the Concorde's 4500 miles. I.e. unfortunately there seems to be no current tech (or coming right tomorrow morning) that will allow Trans-Pacific.

It looks more feasible to me that Starship suborbital SFO-to-Shanghai will come well before a new Concorde on that route. Especially considering that Starship's ballistic trajectory is more fuel efficient on such long distances than supersonic plane flight.