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Background information

Wikipedia says the following on fight distance in relation to fuel consumption overall:

For long-haul flights, the airplane needs to carry additional fuel, leading to higher fuel consumption. Above a certain distance it becomes more fuel-efficient to make a halfway stop to refuel despite the energy losses in descent and climb. For example, a Boeing 777-300 reaches the tipping point at 3,000 nautical miles (5,600 km). It is more fuel-efficient to make a non-stop flight below this distance and to make a stop when covering a longer total distance.

I have heard more about this, and this seems to be the reason that ultra long-haul flights aren't as available as they could be and when they are available they are more expensive (because they are the fastest needing no extra time to stop).

Question

How can a traveler use this knowledge to choose flights more efficiently? Let's say I don't care that much about a longer travel time and don't mind a stopover, how can I compare two flights in terms of fuel usage?

Let's say I'm comparing AMS-BKK and AMS-DOH-BKK (or LHR-SYD to make the issue even more relevant). The first is a direct flight and it's quite a long distance, so it might benefit from a stopover somewhere. Doha is a stopover that divides the route into two equal (almost) legs, so it might be more efficient. On the other hand, Doha isn't on the flight path AMS-BKK, meaning you'll have to travel some extra distance overall (based on the triangle inequality principle).

How can I, as a passenger with internet access and some knowledge (but not all the knowledge that airlines have), compare the fuel use of those two (or any other two) options?

There are of course other factors, for instance, different planes may have different fuel consumption characteristics so some may be more or less efficient on different ranges. Another factor might be that the number of people per flight counts, for example if you're flying alone in the plane then all fuel is spent for you, whereas in a full A380 passenger jet you 'share' the fuel burden among all passangers

Therefore, answers will probably have to use approximations and maybe some assumption, that's fine (though please indicate which approximations or assumptions are used). Answers could consist of (online) tools or rules of thumb (e.g. a comparison based only on the distances of the different legs).

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  • Before you even get to building a planning tool, you'd need to understand the impacts of all kinds of things like altitude (aviation contributes significantly to nitrogen oxides and water vapor in the upper atmosphere), manufacturing (rather than buy new planes, would it be better to use existing ones?), airport efficiency (if a plane has to idle on the ground for 30 minutes idling to get a gate, wouldn't it have been better to fly to a farther, less congested airport?), passenger demand (if you can fill 95% of AMS-DOH-BKK seats but only 85% of AMS-BKK seats), and so on. – choster May 7 '19 at 20:36
  • @choster I'm asking as a passenger, not as a tool-builder or airliner. I get there are many factors to consider, but I'd already be happy with knowing fuel consumption (even if based only on an assumption on fuel usage and the real distances). Working on the assumption that most of those things are equally likely on both options, we'd be left with the distances of the legs. I'd probably be able to figure that out mathematically after looking finding the fuel consumption (over time / weight) and the three distances. It seems like a common problem, so there might already be nice implementations. – JJ for Transparency and Monica May 7 '19 at 20:43
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    I actually sat down a few years ago and tried to work out my carbon footprint (my company has a practice area building life cycle assessment software), and the long and short of it is that flying just isn't green. Reducing my flying went a lot farther than never using air conditioning would have, or not taking hot showers, or never eating red meat. It's a very worthy impulse, but to my mind, debating which flights are better for the environment is like debating which ice cream topping is better for your health. – choster May 7 '19 at 20:50
  • @choster well, the reason I'm asking is that I regularly (yearly or more frequently) have to go from let's say Western Europe to SE Asia. Flying is by far the most convenient so that is going to happen. Then there's the price, and different airlines are quite competitive so there's a lot of choice. Therefore, given that I am going to fly, I'd like to know how much impact different routes have. Given that they have so much impact overall, saving only 5~30% is already better than not having it. – JJ for Transparency and Monica May 7 '19 at 20:58
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    @JJJ Missed that. Well, the OP could rewrite it and play pilot ;-) – user40521 Aug 27 '19 at 7:36
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This is not doable ahead of the time because of the wind. While airlines somewhat care about the wind as it can disrupt their schedules, on the larger scheme of things it doesn't affect them that much because if a flight from A to B consumes more fuel because of a headwind then the return flight will consume less because of the tailwind. And they know a lot more on the day of the flight on how much to fuel to fill the birds with than you can know months ahead when booking how the wind will be on one route or the other.

If you want to be environemnt friendly then buy local and convince others to buy local. Ships are responsible for about 20% of all pollution. A single cargo ship easily pollutes as much as fifty million cars. If you manage to decrease demand so much to take one of those off the seas, that's a huge win. And since almost all that pollution happens out of sight thus out of mind, there's little political will ending it so it's up to us to vote with our wallets.

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  • Isn't that too simple? Surely, wind is less of a factor than a few extra take-offs and landings and a couple thousand kilometer detour? I'm thinking there's some trade-off where an extra stop (take-off+landing) outweighs a certain distance in detour. My question is what that trade-off is approximately and if there's some rule of thumb or calculator for it. And as you say, wind mostly averages out in the end. – JJ for Transparency and Monica Aug 26 '19 at 22:10
  • Wind can easily speed up a flight by 20%. It is huge. The record is like 200 mph tailwinds with about 460-580 mph normal cruise speed. – chx Aug 27 '19 at 0:48
  • If that's the case they should find some way to capture that energy and use it for good. ;) – JJ for Transparency and Monica Aug 27 '19 at 0:50
  • Either you can predict the effect of wind ahead of time, even with a large error (because there is some regularity in wind patterns) or you can't and then it wouldn't impact what the OP has in mind, precisely for the reasons you detail at the end of your second paragraph. – Relaxed Aug 27 '19 at 13:41

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