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Comment by bombcar | Hacker News Reader

That becomes the main issue, the Concorde as it was had 26,400 gallons <=> 95,680 kgs of fuel, and would need more than double that (likely) to do the flight in one go (bar major improvements to efficiency, and counting that more weight at takeoff needs more weight of fuel to fly that extra weight).

A quick search says about 40 minutes to refuel a jet, so a stopover is going to add at least an hour, probably more because they have to come out of supersonic, etc.

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And how are these numbers in subsonic flights?

A flight from London to Singapore. How much fuel would it need without stops, versus how much fuel in the least-fuel case (but more-stops case)?

One thing to take into account is that landing and taking off is very wasteful with fuel - jet engines use significantly more fuel when running in dense air and that doesn't include increased power for climbing.

I'm sure there's someone who can plug in numbers into a flight planner here, I'm interested in actual numbers.

OK, sure, I plugged this into a sim flight planner (http://onlineflightplanner.org/). This is on a Dreamliner.

    Heathrow - Changi: 63933 kgs
    
    Heathrow - Tehran: 26957 kgs
    Tehran - Changi: 39580 kgs

So at least based on this it's not too much of a difference, only 4% more with a stop. (Tehran looked to be roughly in the middle on the flight plan between London and Singapore.)

Interesting, I'd expect it to be a larger difference considering how much the carriers avoid stopovers.

Maybe the fees and organization of refueling tips the balance?

Carriers don't want to do a stop unless they're offloading and onboarding passengers, so they'd rather run one flight to the intermediary, and another direct.

Well yeah, we're talking a about WHY it's a problem for them to stop.

IIRC airframe lifetime is rated in pressurization cycles.

It adds a surprising amount of time. You have to descend, land, taxi to a fueling area, refuel, taxi, take off, climb. And that's if the local regulations allow fueling with passengers on board.

That's probably around 2 hours extra. And this in turn can require the plane to carry additional pilots and flight attendants.

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