Published on September 24th, 2013 | by Guest Contributor


Why Is There Such a Big Fuel Efficiency Gap Between Airlines?

September 24th, 2013 by  

Originally published on Think Progress.
By Ari Phillips.


It’s hard to imagine modern life, let alone the modern economy, without aviation. Yet some airlines generate more greenhouse gases to fly the friendly skies than others.

Demand for air travel has been rising as developing economies expand and incomes increase. This also means greenhouse gas emissions will rise by a projected four percent annually through 2050, by which time they might contribute as much as 15 percent to CO2 emissions.

While the heavy emissions toll of flying may be well known and acknowledged, a new study by the The International Council on Clean Transportation (ICCT) provides a closer inspection by ranking the efficiency of domestic operations by America’s major largest carriers. According to the ICCT it is the first such analysis to adjust for variations in business operations, networks, and scale to provide the fairest comparison possible.


The fuel efficiency gap between best and worst airlines is 26 percent, with Alaska Airlines, Spirit Airlines and Hawaiian Airlines — relatively small carriers serving geographically limited markets — leading the pack. Allegiant Air, the least efficient airline in the ranking, also happened to have the most profitable domestic operations during the 2009 to 2011 period of review.

The obvious upshot, and conclusion of the researchers, being that the financial benefits of fuel efficiency have not yet led to changes across the industry:

“Fuel prices alone may not be a sufficient driver of in-service efficiency across all airlines…. Fixed equipment costs, maintenance costs, labour agreements, and network structure can all sometimes exert countervailing pressures against the tendency for high fuel prices to drive efficiency improvements.”

Factors influencing efficiency are about one-third design and technology-related and otherwise include things like seating density, occupancy, and fueling and how the planes taxi.

Aviation is responsible for about ten percent of global transportation-related oil use, amounting to around 4.5 million barrels per day — a level of consumption that is expected to at least double by 2030.

In a follow-up article to the study, the ICCT compares the carbon intensity of flying to other modes of transportation.

By comparing emissions for a mid-distance, interurban trip, they found that planes are the most fuel-intensive transport option at about 40 passenger miles per gallon gasoline equivalent (MPGge). The most energy-efficient option was to take a bus, at about 124 passenger MPGge. Rail and cars were about the same, at 51 and 53 MPGge, respectively. The number for a car is based on having 2.2 people in the car on average, so is significantly higher if you’re travelling alone.

Fuel economy of various U.S. transport modes on 300 to 500 mile trips.Fuel economy of various U.S. transport modes on 300 to 500 mile trips.CREDIT: ICCT

The authors acknowledge that aircraft offer the considerable advantages of speed, range, ability to cross water, convenience and even safety. However, the skies could be a lot more climate friendly, as the International Civil Aviation Organization has concluded that fuel efficiency of new aircraft can be increased by 65 to 80 percent for conventional wing-and-tube designs by 2030 given sufficient pressure.

Regardless of increases in efficiency or not, air travel emissions will continue to skyrocket for the foreseeable future.

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  • Wayne Williamson

    I was very surprised to see the train so low. I would have thought it would be at the top. Maybe its the amount of stops and time spent at them…don’t know…

  • Steeple

    Age of planes is a pretty big deal. They guys still flying DC9s//MD80s are grouped towards the bottom.

  • mesophyte

    Did the study consider that the bigger airlines tend to fly to busier airports and hence spend more time in holding patterns waiting for landing/take-off slots? Those eat up a lot of fuel.

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