As part of its ‘Jet Zero’ strategy to ensure the aviation sector meets the national target of net zero emissions by 2050, the UK government is considering whether to mandate the provision of standard, reliable and accurate environmental information to encourage travellers at the time of booking their flights to choose the greenest option. Such information, says the Department for Transport (DfT) in a consultation launched last month, could help passengers make more informed decisions, increase public awareness of carbon emissions and climate change, and support aviation growth in a sustainable manner. New analysis of US domestic routes by the International Council on Clean Transportation (ICCT), which supports itinerary-level emissions disclosure by airlines at the point of purchase, shows the carbon footprint of different itineraries on the same route varies greatly in terms of CO2 emissions per passenger. On average the most fuel-efficient itineraries emitted 63% less CO2 per passenger than the highest emitting itinerary. Greater efficiency also tends to correlate with lower fares, which is a win-win for consumers and the environment, says ICCT.
In its consultation, the DfT reports the UK Civil Aviation Authority recently carried out a research project with consultancy BritainThinks to explore the feasibility and utility of sharing carbon information with consumers. Most participants in the study thought emissions data should be provided to inform the public about the relative impacts of flying, allow the opportunity for consumers to pick more sustainable flight options and also encourage airlines to reduce emissions. The participants considered the information should be standardised, easily accessible and have third-party vetting to encourage trust and reliability.
ICCT points out that travel search engines like Google Flights, Kayak and Skyscanner have introduced ‘eco-flight’ filters into their platforms, reflecting, it says, growing consumer interest in climate disclosure at the time of purchase.
A study which included a survey of employees at the University of California also found that when presented with hypothetical price and emissions estimates side by side, the employees expressed a willingness to pay more for a lower-emitting flight – representing about $200 per tonne of CO2e saved, which is much higher than carbon offset prices seen today. The emissions information also 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.
The ICCT’s own study shows flights with the lowest emissions per passenger are not necessarily the most expensive. “Consumers might worry that lower-emitting flights cost more, but our analysis has shown that in most cases the least emitting flight is among the cheapest tickets on a route,” Sola Zheng, co-author of the study, told GreenAir. “With access to emissions data, consumers can opt for fewer emissions with the same amount of dollars.”
ICCT says although there are a number of online carbon calculators available, including from ICAO, that allow users to estimate CO2 emissions for origin-destination airport pairs, they do not provide specific information on carrier or aircraft type and cannot be used by consumers to choose less-emitting flights.
Its study analysed 20 frequently travelled US domestic routes, 16 of which were selected based on the high number of departures and total revenue passenger-miles in 2019. On the remaining four routes, low-cost carriers accounted for more than 60% of market share and were selected based on the number of departures in 2019 as well as on carrier diversity.
Among the analysed routes, the least-emitting itinerary on average emits 63% less CO2 than the most-emitting itinerary on the same route, with a range from 48% to 80%. The emissions gap between the most and least emitting itineraries is much wider than the airline-level fuel efficiency gap of 26%, reflecting the influence of layovers (direct vs. non-direct flights), aircraft used and variations in operational parameters like load factors. When compared to the route averages, the least-emitting itineraries are on average 22% less carbon-intensive.
In general, the data confirmed that a nonstop flight is likely to emit less CO2 per passenger than an itinerary with layovers. However, found the study, there can be relatively fuel-inefficient nonstop flights that emit more than some one-stop itineraries on the same route, so the number of stops does not always identify lower-emitting itinerary options.
The correlation between itinerary emissions and aircraft deployed is also complicated, says ICCT. Comparing the combined fuel efficiencies of multiple aircraft based on their types alone yields high uncertainties and is not easily done by an average consumer. Even for nonstop flights, the relative emissions of different itineraries using the same aircraft type vary depending on operational factors and on the other types of aircraft flown on the route. Itineraries on the same aircraft can be low-emitting on one route but high-emitting on another.
The carrier that operates the aircraft also matters. An airline may carry more passengers on a given flight, either by operating at higher load factors or via a single class service, leading to lower per-passenger emissions than other carriers flying the same aircraft on that route. “Load factors, aircraft age, congestion at a hub airport and many other factors also contribute to the different outcomes for the same aircraft type,” says the study. Despite the variation across routes, however, flights using the newest generation of aircraft types are likely to be less emitting regardless of other factors.
The study also found the lowest-emitting itinerary by a carrier sometimes emits more than the route average, indicating that loyalty to a single airline could lead a consumer to choose a higher-emitting itinerary than necessary. “There is no one carrier that operates only low-emitting itineraries (better than route average) across all the analysed routes on which it operates,” it explains. “An airline can also emit much less than airlines on one route but show the opposite emissions pattern on another route. Some airlines have more fuel-efficient operations than others on average but there is no one ‘greenest’ airline when evaluated at the route and itinerary level.”
Said Zheng: “There are no golden rules when it comes to selecting lower-emitting flights based on aircraft type or airline. For two flights from Los Angeles to Hawaii, for example, one may emit 63% less CO2 than the other on a per passenger basis but consumers currently have no access to this kind of information. Directly disclosing emissions by itinerary would be the most helpful to them.”
Emissions disclosure by airlines would raise awareness among consumers of their carbon footprint and, more importantly, reward airlines that operate more fuel-efficient flights through strategies such as deploying newer, more fuel-efficient aircraft and improving load factors, argue the authors. “Eventually, as technologies such as sustainable aviation fuels and zero emission planes fuelled by electricity and/or hydrogen become mature, emission reductions due to fuel switching and cleaner aircraft could be rewarded as well,” they add.
While in principle airlines could disclose the carbon intensity of their flights voluntarily on their own websites or other booking platforms, the authors suggest public policy would help to ensure accurate and standardised disclosure from all airlines. For example, policymakers could require carriers to disclose previous-year emissions by route and aircraft on their websites, with third-party booking sites also choosing to display independently validated and credible information to consumers.
“The flip side of voluntary behaviour change by consumers is to internalise the environmental costs of flying into ticket prices through taxation policies or market-based emissions regulations,” say the authors. “While effective, experience suggests that these policy instruments are politically difficult and may take a long time to craft and implement. Emissions disclosure, on the other hand, could conceivably be implemented in a shorter period with fewer resources because it is politically less fraught.”
Photo: Skyscanner’s ‘Greener Choices’ labels flights it believes to emit less CO2 compared to the average