If your flight time is half, you can run twice as many flights per day with the same plane, which halves your amortized capital cost per flight. That doesn't get you all the way there, but it's a significant cost reduction, which combined with others, could conceivably get you there.
> If your flight time is half, you can run twice as many flights per day with the same plane
Certainly not. Planes don't spend all their time flying. A significant part of the time they are being boarded or people are stepping out, and freight is being loaded and unloaded, and the plane is service, fuel tanks are filled, catering material brought in, wings are de-iced. Some of these activities happen at the same time with each other, but many of them not.
Planes don't spend all their time flying. A significant part of the time they are being boarded or people are stepping out, and freight is being loaded and unloaded, and the plane is service, fuel tanks are filled, catering material brought in, wings are de-iced.
The turnaround time -- time needed for everything that happens from when the plane arrives at the gate to when it departs again -- is only comparable to flying time for smaller aircraft doing shorter domestic hops.
For aircraft doing the kinds of inter-continental segments a supersonic airliner is targeting, there's no real comparison. And airlines most certainly do optimize for time spent in the air; a plane on the ground is a plane making no money. So you see a single aircraft bounce around among a bunch of hubs all in one day, for example, or larger, longer-range aircraft doing rotations of where they fly to (like having the same aircraft do a flight from the US to South America and back, then off to Asia and back, to optimize for arrival/departure times and minimize time spent not flying)
Of course airlines optimize it, but still, boarding alone takes a significant portion of the total time needed for a long-haul flight.
If I look at the latest long-haul flight I took, the flight time was 11 hours, turn-around time at airport 4 hours, for a total of 15 hours. If you'd drop the flight time to half, and manage to do accelerate boarding, cleaning, re-fueling etc in 3 hours, you'd come up with 8.5 hours. Much better, but not even close to be able to deliver twice as many flights per day. It'd be more like a 50 % improvement.
Long-haul utilization also depends on one other factor, which is time zones. It can be worth leaving the plane on the ground longer in order to line up for a more desirable departure/arrival time.
You see this a lot with transatlantic flights, where they spend more time than necessary on the ground at each end, but doing so sets up better timing (like eastbound TATL flights departing in North American evening and arriving in European morning).
Those are marginal costs. Parent comment was talking about amortised costs, i.e. fixed costs. Such as the airplane, itself (depreciation per mile of flight aside, but that’s another point).
IIRC lifetime ratings on aircraft are most heavily based on the number of pressure cycles the airframe receives, i.e. the number of flights it does, not the length of time it spends in the air or its age. So being able to do twice as many flights in the same time just shortens the lifetime of the aircraft.
