Which Flight You Choose Has a Huge Impact on Emissions

There's merit in mandating airlines to report emissions by itinerary.

airplane in flight

Aaron Foster / Getty Images

Air travel has an undeniable carbon footprint: some estimates suggest roughly 2.4% of global carbon dioxide emissions come from commercial aviation and passenger aircraft emissions increased 33% between 2013 and 2019.

When I interviewed Dan Rutherford— Program Director for the International Council on Clean Transportation’s (ICCT)—we discussed whether the pathway to lower aviation emissions involved supply-side improvements to efficiency and fuel choice, or demand-side reductions in flying. Unsurprisingly, he told us the answer was both/and, and not either/or. He also suggested that, in addition to avoiding unnecessary flights entirely, travelers could have a big impact by simply choosing lower emissions itineraries, even between the same two airports. 

Digging deeper into this question, the ICCT has just released a new study—lead-authored by Xinyi Sola Zheng and co-authored by Rutherford—showing the huge potential for consumers to reduce carbon dioxide emissions on their trips.

Key findings of that study include: 

  • Across 20 representative routes, a traveler choosing the lowest emitting flights would be responsible for 22% lower emissions than the average flight, and 63% lower than the highest emitting flights.
  • In some cases, the difference was even starker: The team found as much as 80% difference in emissions on flights between Orlando and Philadelphia.
  • While following rules of thumb, like flying direct and on newer aircraft, can help consumers choose less-emitting flights, they are not foolproof or 100% accurate. Other variables, including load factor and seating configuration, also impact the carbon intensity of a trip. 
  • While some carriers are more fuel-efficient than others, no airline operated low-emitting flights on all routes in 2019. 

The table below shows just how large a variation there is between the highest and lowest emitting flights. In fact, of all 20 of the routes analyzed, only one showed less than 50% difference between the lowest- and highest-emitting itinerary. 

The table below shows just how large a variation there is between highest and lowest emitting flights.

According to the report’s authors, these findings point to the significant potential of mandating airlines to report emissions by itinerary. While they note more research is needed on the specific impact on consumer behaviors, they do reference a study by researchers at the University of California, Davis, in which university employees were asked to evaluate flight preferences when price and emissions were listed side-by-side: 

“The surveyed employees expressed willingness to pay more for a lower-emitting flight—about $200 per tonne of CO2-equivalent of emissions saved, which is much higher than the carbon offset prices seen today. The emissions information also reportedly provided more incentives for the employees to choose direct flights from a non-preferred airport over flights with a layover leaving from a preferred airport.”

As someone who has tried to develop a workplace plan for lower carbon travel, it occurs to me that such labeling would also provide benefits to the growing number of companies and organizations that are trying to manage their institutional carbon footprint. By creating easy-to-access reporting on the specific emissions of specific flights, it would become significantly easier for businesses and institutions to require or reward lower carbon travel choices for work-related flights. 

Business owners, accounting department managers, and folks who are simply on a budget will also be pleased to know that on three-quarters of all routes analyzed, the least emitting flight was also one of the cheapest, and a consumer could reduce emissions by up to 55% by choosing a ticket from within the cheapest 25% of fares. 

Yes, flying less or not flying at all is an excellent way to help fight the climate crisis. Yet speaking as someone who still flies home to England to see my mum, I would appreciate knowing which routes are going to do the least amount of damage. 

View Article Sources
  1. Graver, Brandon, et al. "CO2 Emissions from Commercial Aviation, 2018." The International Council on Clean Transportation, 2019.

  2. Graver, Brandon, et al. "CO2 Emissions from Commercial Aviation: 2013, 2018, and 2019." The International Council on Clean Transportation, 2020.

  3. Zheng, Xinyi Sola, and Dan Rutherford. "Variation in Aviation Emissions by Itinerary: The Case for Emissions Disclosure." The International Council of Clean Transportation, 2021.