Every single other major jet manufacturer is already making air travel cheaper and more efficient every year. It's all airlines who buy from Boeing or Airbus care about. The underserved niche is premium and small, not scale. Commercial aircraft will get 1% more efficient every year with or without new companies (https://en.wikipedia.org/wiki/Fuel_economy_in_aircraft#/medi...).

If we start in supersonic today, and innovate at the same pace for 20 years, you might match the efficiency boom from the "jet age" and make supersonic twice as efficient as today.