Rendering of an efficient airplane concept design.
Technical Summary

Efficient Aviation

Project Drawdown defines the efficient aviation solution as the increased use of technologies to reduce aircraft fuel burn. This solution replaces conventional aircraft with existing global fleet-wide fuel efficiency.

In 2005, all of aviation’s share of global warming was 4.9 percent despite being only 2.2 percent of carbon dioxide emissions in that year[1]. This is due to aviation’s generation of other climate pollutants besides carbon dioxide that also cause warming. Considering aviation fuel consumed in 2016[2], and all global carbon dioxide emissions in 2016[3], all aviation is estimated to have caused approximately 2.6 percent of manmade carbon dioxide emissions in 2018. Growth in aviation’s share is causing increasing alarm. Airplane fuel efficiency efforts aim to reduce fuel use per passenger-kilometer of air travel. Though freight-only aircraft fuel efficiency is not analyzed here, part of the impact on air freight fuel use is accounted for in the large fraction of total air freight that is carried in the belly of passenger aircraft.[4]

There are numerous technologies and operational approaches for reducing airplane fuel use; only the most impactful technologies in use today to improve fuel efficiency were included in this study. Therefore, well-publicized but noncommercial technologies such as aviation biofuels were excluded.


This analysis includes the newest, most fuel-efficient aircraft (called “intermediate generation”),[5] as well as the use of fuel efficiency retrofits to existing aircraft. Intermediate generation aircraft are expected to be 15–20 percent more fuel-efficient than earlier models, in part as a result of more fuel-efficient engines, new wingtip devices,[6] and light weighting approaches. Research suggests that the combination of these three technologies in a retrofit would amount to efficiency improvements comparable with a newer aircraft model. In this study, new and retrofitted aircraft are compared to conventional aircraft with the existing global fleetwide fuel efficiency.

Total Addressable Market[7]

The total addressable market for efficient aviation is measured in terms of total interurban passenger travel by air, projected for every year of analysis (2020–2050), in billion passenger-kilometers. Current adoption[8] was taken as the total passenger-kilometers provided by existing intermediate generation aircraft, in the single-aisle and twin-aisle categories.

Projected adoption of fuel-efficient aircraft was based on the expected production of intermediate generation aircraft, according to published delivery rates of major suppliers.[9] Delivery rates were assumed fixed for each aircraft type.

Adoption Scenarios

Impacts of increased adoption of efficient aviation from 2020 to 2050 were generated based on two growth scenarios, which were assessed in comparison to a Reference Scenario where the existing fraction of higher-efficiency aircraft remains constant.

  • Scenario 1: Fuel burn is improved by 13 percent, Boeing and Airbus supply aircraft at their published rates, and an additional supplier starts adding comparably efficient aircraft to market[10]. One hundred aircraft are retrofitted annually.
  • Scenario 2: Fuel burn is improved by 18 percent. Aircraft delivery rates, retrofitting, and retirement are similar to the Scenario 1. Global load factors increase to 83 percent (U.S. average).

Emissions Model

Emissions for each scenario were estimated using the fuel emissions factor taken from the Intergovernmental Panel on Climate Change (IPCC) guidelines, and applied to fuel consumption data from the International Council on Clean Transport (ICCT).

Financial Model

Costs of adopting the intermediate generation aircraft are reported as the additional cost compared to adopting aircraft with average fleet efficiency. For each intermediate generation aircraft, an equivalent conventional aircraft was priced and the price difference was derived.[11] The average difference for single-aisle aircraft was around US$11 million,[12] and that of twin-aisle was US$40 million.[13] Operating costs, which included fuel costs, were derived using historical data from the International Energy Agency (IEA).[14] The solution’s operating costs were reduced by the efficiency improvements noted above.


To prevent double-counting, steps were taken to ensure that the total travel demand of all non-urban passenger Transport Sector solutions remained below the projected total non-urban travel demand.


In Scenario 1, a potential reduction of 6.3 gigatons of carbon dioxide-equivalent greenhouse gas was found from 2020 to 2050, which corresponds to an 80 percent adoption rate by 2050. Net costs over that time would be US$863 billion above the conventional approach. Efficiency improvements are estimated to bring lifetime operating savings of US$2.5 trillion[15], however. For the Scenario 2, the emissions avoided amounted to 9.2 gigatons with 85 percent adoption.


The use of more efficient aircraft is desirable for airlines in times of higher fuel prices. It would have direct bottom-line impacts, as fuel often represents a third of operating costs. Since 2015, however, fuel prices have been relatively low, and there is no assurance that prices will return to their previous levels of almost three times higher. At these lower fuel prices, the financial attractiveness of these aircraft efficiency improvements is not great, and in some cases result in negative net present values for airlines according to our calculations. However some of this may change with the coming implementation of the  Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) program. To some extent, inclusion of fuel switching approaches such as aviation biofuels can help reduce the need for aircraft technology improvements.


There are limitations to this approach. For example, the potential of other technologies being implemented was excluded in this study.[16] Also, the Reference Scenario conservatively assumes fixed fleet efficiency. These limiting assumptions were made to show the impact of existing technologies on the airline industry. The results indicate that airlines have a role to play in the planet reaching the point of drawdown.

Note: August 2021 corrections appear in boldface.

[1] Lee, D. S., Fahey, D. W., Forster, P. M., Newton, P. J., Wit, R. C., Lim, L. L., ... & Sausen, R. (2009). Aviation and global climate change in the 21st century. Atmospheric Environment, 43(22-23), 3520-3537.

[2] From OECD/IEA (2018) World Energy Balances 2016, OECD/IEA, Paris

[3] From Global Carbon Atlas (2018) CO2 Emissions, Global Carbon Project,

[4] According to Airbus, belly freight is about 52 percent of all air freight.

[5] Including the 787, 777X, and 737MAX family of Boeing, and the A320neo family, A330neo family, and A350XWB of Airbus.

[6] Also called “winglets” or “sharklets”, these devices cannot be installed on all older aircraft due to lack of sufficient wing strength and other limitations.

[7] For more on the Total Addressable Market for the Transport Sector, click the Sector Summary: Transport link below.

[8] Current adoption is defined as the amount of functional demand supplied by the solution in 2018. This study uses 2014 as the base year due to the availability of global adoption data for all Project Drawdown solutions evaluated.

[9] Delivery of a single-aisle aircraft is assumed to provide 247 million passenger-kilometers, and a twin-aisle aircraft 840 million passenger-kilometers, of adoption.

[10] This additional manufacturer can represent any or all of numerous nascent options, such as COMAC of China or the UAC of Russia. It produces around 5 percent of all efficient aircraft annually.

[11] For instance, the Airbus A320neo was considered a more efficient replacement for the A320, and the Boeing 777X-9 was considered a replacement for the 777-300ER. These relationships were determined through web searches for each efficient model.

[12] All monetary values are presented in 2014 US$.

[13] It is assumed that this differential represents the retrofit costs for each aircraft type, and acknowledged that airlines often pay different prices than the list prices due to negotiations that occur with the manufacturers.

[14] The fuel prices (2007–2018) were averaged, and this fixed average was used for the future projections.

[14] The net operating savings for the full lifetime of all units installed during 2020–2050.

[16] The potential for open rotor engines could be large, but estimates seem to indicate availability in the 2030s onward.