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How to choose connecting flights to minimize environmental impact

by Michael Sivak.

Because of the long distances typically involved in flying, your next airline trip will likely contribute a substantial amount of greenhouse gas emissions. Obviously, to minimize the emissions, taking a nonstop flight is the way to go because that will result in the shortest distance flown. However, if a nonstop flight is not available, choosing the connecting flights with the shortest total distance flown can make a lot of difference. This is the case because the range of possible distances (and thus emissions) can be substantial even for connecting flights that do not vary greatly in terms of the total trip time.

When one shops for airline tickets, the cost is usually the dominant consideration. Other factors of importance frequently are the schedules of the flights, and one’s loyalty to a specific airline because of frequent-flyer perks. For trips involving connecting flights, an additional consideration involves the total trip time. However, for those flyers who care about their environmental impact, the total distance flown on trips requiring connecting flights should be of primary concern. (Because of varied layover durations, there is no perfect correlation between the total distance flown and the total trip time.)

As examples of the ranges of distances involved for airline trips, I provide here information about the total trip lengths for flights from Detroit (my nearest airport) to the airports nearest to my three favorite national parks (Fresno for Yosemite, Kalispell for Glacier, and Jackson WY for Grand Teton). None of these three destinations can currently be reached from Detroit by nonstop flights.

The flight schedules as of July 29 were obtained from Google Flights. The desired trip date entered into the search was August 14. The distances flown for each segment came from Web|Flyer. Of interest were all connecting flights with one layover that were not more than a third longer in terms of the total trip time than the shortest possible connecting flights. There were 12 connecting flights to Fresno that met these two constraints, as well as 14 to Kalispell and 12 to Jackson. The number of unique connecting airports was 7 for Fresno, 6 for Kalispell, and 5 for Jackson.

As shown in the table below, for each city pair, the connection with the longest distance flown is substantially longer than the connection with the shortest distance flown. The maximum additional distance flown is 36% for Detroit to Fresno, 54% for Detroit to Kalispell, and 55% for Detroit to Jackson.

Sivak *Not more than a third longer in total trip time than the shortest connection.



So instead of feeling guilty and just paying carbon-dioxide offsets for your sins, spend additional money—if needed—on the shortest possible distance to be flown each time you have to take connecting flights. It is better not to emit carbon dioxide in the first place than to try to remedy the consequences of doing so. The legwork required to obtain the information for a responsible decision is minimal.


Michael Sivak is the managing director of Sivak Applied Research and the former director of Sustainable Worldwide Transportation at the University of Michigan.

Comments

GdB

Two other very import factors:
(1) Newer more efficient mid range airplanes have reduced fuel consumption a lot over older airplanes.
(2) Shorter flights carrying less fuel are lighter and therefore burn less. Read about the breguet range equation...

Long range airplanes burn more fuel to carry extra fuel and structure.

All airlines could reduce their carbon footprint easily by flying with navigation computer set at Cost Index = 0. Carbon fees will encourage this.

Eventually the greatest carbon reduction could be by flying electric powered airlines with multiple stops. Much of the decent energy can be recovered, or utilized to glide to the destination.

Lad

Airplanes have been pretty much skating up until now. Finally, someone is shining light on the facts about "How dirty jet engines really are.'' Now, what can they do about the problem; reading this article, I would say at this point ; 'Not, Much.' But, one must realize this is a profound problem since at any one point in time , there are 30,000 aircraft flying above us and all are polluting the atmosphere.

HarveyD

Use ultra high seep e-trains instead?

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