…Incidentally such an outcome also leaves programs like MS-21 with the best possible competitive environment, at least if they can execute on time to get the largest window before new clean-sheet designs eventually come out from Airbus and Boeing.

I know what I’d do if I were COMAC or Irkut.

Have a design Mach number of 0.6-0.65.

Take the hit on speed and have a more fuel efficient aircraft.

Don’t try and beat them on their home patch. Set up camp somewhere else and see if the airlines bite. Given the price of fuel – I firmly believe most airlines would swap a 20% decrease in speed for a 10% decrease in fuel consumption.