Road to Net Zero

Achieving our Net Zero goal will require a range of different approaches to the four pathways in our climate strategy – Reduce, Innovate, Remove and Collaborate. But we believe that doing so, with consistency and commitment, will reduce our net emissions to zero by 2050 without the use of traditional carbon offsets.

United’s Greenhouse Gas Emissions Footprint

We have evolved our reporting to align with corporate best practices around GHG accounting protocols, including anticipated updates in accounting guidance from Science-Based Targets Initiative and Greenhouse Gas Protocol. This revised reporting methodology allows us to provide greater transparency around the aircraft’s GHG emissions from burning conventional jet fuel and Sustainable aviation fuel (SAF).

Our 2022 GHG footprint now incorporates a new Scope 3 category: GHG emissions from conventional jet fuel production, referred to as “well-to-tank” (WTT) emissions. With this update, we now capture the full lifecycle emissions of conventional jet fuel usage, i.e. the “well-to-wake” (WTW) emissions which allows us to chart both Scope 1 and Scope 3 emissions reductions from conventional jet fuel. SAF lifecycle emissions are also reported on a WTW basis, with biogenic emissions from SAF combustion reported as a separate, non-scope line item.

Well-to-tank: ~20% (fuel production); tank-to-wake: ~80% (fuel used by aircraft)

United’s 2022 GHG emissions are summarized in the table below.

Carbon Emissions1


Direct (Scope 1) GHG Emissions in Metric Tons CO2e


Gross GHG emissions


Biogenic Emissions (Outside of Scopes) in Metric Tons CO2e


Indirect Emissions in Metric Tons CO2e


   Indirect (Scope 2) GHG emissions


   Other indirect (Scope 3) GHG emissions


Total GHG Emissions in Metric Tons CO2e


   Gross GHG emissions


   Carbon offsets (a)

   Net GHG emissions


Educating our customers

In February 2023, we became the first US airline to show customers an estimate of their flight’s carbon footprint when booking, on a per economy seat passenger basis. We believe transparency with our customers is important as we embark on our transition toward more sustainable flying.

Example of carbon footprint in kg CO2 shown on flight res

What is Sustainable Aviation Fuel (SAF)

Sustainable Aviation Fuel (SAF) is an alternative to conventional jet fuel. Its potential to scale is due to its ‘drop-in’ readiness, which means it can be used in current operations with existing infrastructure – no changes to fuel systems or aircraft engines required.

While combusting SAF still releases CO2, like conventional jet fuel, the production of SAF generates much lower emissions than the production of conventional jet fuel, as SAF is made from renewable materials (referred to as feedstock), rather than drilled fossil oil. United’s current SAF suppliers use feedstock like waste fats and used cooking oils and greases, which are otherwise considered waste to make SAF. This process reduces emissions from SAF up to 85% on a lifecycle basis compared to conventional jet fuel, lowering the emissions across our value chain and operations.

Lifecycle Comparison of Conventional and Sustainable Fuel

Conventional jet fuel: releases new carbon into the atmosphere

  • Extract: crude oil is extracted from the ground
  • Refine: crude oil is refined into jet fuel, a carbon intensive process
  • Consume: finished jet fuel is used to fly aircraft

Sustainable aviation fuel: emits up to 85% less carbon on a lifecycle basis

  • Process feedstock: renewable materials are collected as SAF feedstock
  • Refine: feedstock is converted to fuel using as much renewable energy as possible
  • Consume: finished product is tested to prove identical to jet fuel and used to fly aircraft
  • CO2 emissions from flying are returned to renewable materials

The waste fats, oils and greases that are used to produce our SAF today will not meet demands across the industry, as they are in limited supply. As the SAF industry scales, additional feedstock accompanied by different conversion technologies will need to be commercially deployed to continue to increase supply for the industry.

SAF Throughout Our Roadmap


Today’s commercial SAF

2nd generation SAF

3rd generation SAF


Currently used feedstock





Waste fats, oils and greases

Alcohols (ethanol)

Biomass and biogenic waste sources (e.g., MSW2)

Non-food crops, Captured CO2 and clean hydrogen

Conversion Pathways


Hydroprocessed esters and fatty acids (HEFA) is a mature, commercially available technology.  

Alcohol-to-jet (ATJ)

Pathway that converts commercially available alcohols (e.g., ethanol) to SAF.

Thermochemical conversion pathways3

Biomass feedstock removes greater amounts of carbon from the atmosphere during growth and harvesting, and municipal solid waste (MSW) feedstock is diverted from the landfill where it would otherwise emit more GHGs like methane. These lower-carbon feedstock can be converted to SAF but will take more time to build the facilities to commercially supply the market.

Cellulosic crops and captured CO2, with clean hydrogen, (called power-to-liquids), could one day result in carbon-negative SAF because of the amount of carbon removed from the atmosphere that is embodied in the feedstock exceeds the amount emitted during production and combustion.

Although current production has helped establish SAF in the market, it is in limited supply. The International Air Transport Association (IATA) estimates that in 2022, approximately 79 million gallons (300 million liters4) of SAF were produced. By comparison, in 2022 IATA estimates airlines globally used 19 billion gallons (73 billion liters5) of fuel. That means that the entire global SAF supply represents less than 1% of the world’s fuel usage.

United recognizes that while the SAF volumes available in the market today are insufficient for the decarbonization of air travel and that SAF production technologies are not widely available yet, scaling SAF is critical to achieving net zero. Our roadmap to reduce our GHG emissions from jet fuel will help us chart a more sustainable course for the future of air travel and United continues to signal its leadership through targeted initiatives that will help signal demand for SAF.

Our progress so far on Sustainable Aviation Fuel

  • 2013 – First definitive, ongoing SAF purchase agreement by an airline globally
  • 2015 – Largest investment of SAF
  • 2016 – First ongoing use of SAF on flights out of Los Angeles International Airport
  • 2020 – First commitment to 100% green by reducing 100% of GHGs by 2050 without relying on traditional offsets
  • 2021 – Launched Eco-Skies Alliance. First passenger flight using 100% SAF in one engine. Established United Airline Ventures
  • 2022 – First International SAF expansion into Amsterdam Airport buy US airline
  • 2023 – First US Airline to publish CO2 emissions for flights and launch Sustainable Flight Fund

United’s decarbonization roadmap 6

Our climate targets are rooted in the belief that, to truly decarbonize the airline, we must address the root cause of our GHG emissions: the jet fuel we use.

To address our GHG emissions from jet fuel, which contributes 98.5%7 of our total GHG emissions today, we believe our opportunities for reductions are through more efficient operations, aircraft fuel efficiency improvements, advanced aerospace technologies that are forecasted to come to market between now and 2050, and the replacement of our conventional jet fuel with SAF.

United Decarbonization Roadmap

(Metric Tons CO2e)

United’s business as usual (BAU) scenario is represented by the top line slope of the forecasted emissions curve in the Roadmap9.

With none of the decarbonization levers employed, United’s gross GHG emissions in 2050 from jet fuel consumption are forecasted to be roughly 90 million metric tons CO2e. The levers illustrated on the Decarbonization Roadmap are all dependent on our assumptions related to future operations, the future commercialization of clean technology solutions, including aircraft and SAF technologies, supportive government incentives and policies, and a broader global economy-wide transition from fossil fuels to cleaner sources of energy10.

It is important to note a few important highlights that differentiate this Roadmap from others. Due to our net zero pledge, carbon offsets are not included within our Roadmap. We also forecast a full phase out of conventional jet fuel use by 2046 with SAF projected to make up over 54% of our expected emissions reductions by 2050. Lastly, we include alternate propulsion to address emissions from regional routes. Although we still expect combusting SAF to release GHGs in 2050, the emissions reductions from our various levers are expected to net those residual emissions from combusting SAF to zero.

Advancements in aircraft design and engine technology continually target improvements in fuel efficiency. We have forecasted a steadily increased fuel efficiency through 2050, through more efficient advanced technologies such as new engines, open rotors, more aerodynamic airframe designs, and future generation aircraft models that are currently in the design phase11. Our estimate is that by 2050, future generation aircraft could be up to 30% more fuel efficient12 than today’s commercial fleet. Additionally, we anticipate the ability to retrofit some of these efficient technologies onto existing aircraft, improving fleetwide fuel efficiency by 1.5% every five years. In our Decarbonization Roadmap, we forecast this lever to contribute approximately 13% of the reductions needed to reduce our BAU emissions to zero.

Beyond future aircraft design, the replacement of older aircraft with newer, more fuel-efficient models, with more seats, results in lower GHG emissions. In 2021, United announced ‘United Next,’ a historic aircraft order of the newest aircraft models today, which is expected to increase the total number of available seats per domestic departure by almost 30%, significantly lowering carbon emissions per seat. As part of the program, United has placed orders for more than 400 narrowbody and widebody aircraft, with options to increase that number to nearly 700 narrowbody and widebody aircraft, with an expected estimated 17-25% improved fuel efficiency per seat, compared to older planes. These new, more efficient aircraft, combined with fuel efficiency measures on seat density result in 20% of our forecasted emissions reductions needed to help us reach net zero by 2050 without the use of traditional carbon offsets.

Beyond the fuel efficiency of our fleet, we also have operational measures to support flying the most efficient and direct routes. Some of these measures are within our operational control, like reducing the use of the auxiliary power unit (APU) in favor of lower-emission solutions like electric power at the gate; and single-engine taxiing, which alone could save up to 5 million gallons of jet fuel annually. Additionally, improvements in the routes we fly —like the FAA’s development of a more streamlined and efficient air traffic control—are expected over time to save fuel not only for United, but all air travel operations. Operational efficiency measures such as these are forecasted to reduce United’s emissions by 8% from BAU in 205013.

As we look forward to 2050, United anticipates most of its fleet will require jet fuel for propulsion, due to its energy density and low weight. However, zero-carbon aircraft technologies like battery electric or hydrogen propulsion may be adopted for shorter-haul distance flights. We anticipate using renewable power to charge aircraft batteries and the electrolyzers used to make green hydrogen for hydrogen propulsion. Using 100% renewable power could reduce full lifecycle GHG emissions for operating these aircraft to net zero. United believes that 4% of our reductions from BAU to net zero will be attributed to the adoption of these alternate propulsion aircraft in our regional operations.

Large scale-up and adoption of SAF is a critical lever to achieving our climate targets14. The SAF levers represented in the Roadmap reflect the transition we anticipate in the mix of SAF that we will adopt to drive lower reductions across our value chain:

  • Today’s commercial SAF pathways: Currently, all commercial-scale SAF production is made from fats, oils and greases, which are limited in global supply and have a limit to the achievable amount of lifecycle GHG reductions (currently up to 85% reduction of lifecycle GHG emissions). With current feedstock constraints, today’s most mature technology cannot be relied upon in full to meet our SAF demand through 2050. United continues to invest in technologies that can unlock more feedstock for this mature conversion pathway but recognizes it will remain limited in supply through 2050. This SAF has a prominent role in decarbonizing our emissions (contributing 17% of the forecasted reduction in 2050) but is not the only type of SAF we aim to use.
  • 2nd generation SAF: The largest portion of our SAF mix in 2050 is forecasted to be the next generation of SAF conversion technologies, which can utilize existing bioproducts, like today’s ethanol, or convert types of biomass made from sources like forestry waste, fuel crops, municipal solid waste, and advanced alcohols (i.e. cellulosic ethanol) to fuel. These feedstock sources, often viewed as waste materials, are much more widely available today and could result in greater lifecycle GHG reductions than today’s commercially available SAF.
  • 3rd generation SAF: SAF pathways will continue to emerge as we approach the final decade of our Roadmap and the broader economy transitions to scale up cleaner energy technologies. We believe technologies, including carbon removals, may produce carbon negative SAF15. To reach net zero using this 3rd generation of SAF, we assume that the existing blend limits required for SAF usage will be removed over time to facilitate the adoption of 100% SAF usage, demonstrated by our forecasted 100% SAF usage with conventional jet fuel fully phased out by 2046. We anticipate commercial availability of such technologies by the 2040s, as these technologies are reliant on several factors that do not currently exist at scale, including an economy-wide transition to 100% renewable energy, further development of 3rd generation SAF production infrastructure, and ASTM approval to increase SAF blending limits.

You’ve probably heard of carbon offsets. While they may offer customers some peace of mind, traditional carbon offsets ...simply don’t meet the scale of this global challenge… It’s just not realistic to think we can plant enough trees to start bending that curve today. I believe the world and the airline industry has to be bolder.

Scott Kirby CEO

No Offsets Pledge

United has pledged a net zero goal of becoming 100% green by eliminating our GHG emissions by 100% by 2050 without relying on the use of traditional carbon offsets.

United is committed to achieving our climate targets without the use of traditional, nature-based or voluntary carbon offsets that derive their environmental attributes through avoided emissions or reductions that are both difficult to quantify and easily reversible. We believe that combining in-sector emissions reductions and carbon removals technologies is the credible path forward to address future aviation sector emissions.

Innovative Approaches to Financing Our Transition to Low Carbon Flying

Given the two to four times ‘green premium’ associated with purchasing SAF when compared to conventional jet fuel, United implemented several strategic initiatives to help establish a robust SAF market. From engagement with corporate fliers today, through the Eco-Skies Alliance initiative, to establishing an investment vehicle via United Airlines Ventures, United is taking action to accelerate SAF supply.

Eco-Skies Alliance

The Eco-Skies Alliance, launched in 2021, is United’s innovative program wherein corporate passenger and cargo customers work together to finance the ‘green premium’ of SAF. To date, nearly 40 program participants representing multiple industries are allocated Scope 3 emissions reductions for flying on United in exchange for funding the premium for SAF. Collectively, the program demonstrates a strong market signal that industries beyond aviation demand sustainable air travel. At the end of 2022, customers of the Eco-Skies Alliance had committed to fund approximately 9 million gallons of SAF, which is the same amount of emissions from flying our passengers approximately 600 million miles.

In collaboration with our corporate customers, United flew the first passenger flight using 100% SAF in one engine in December 2021. The historic flight departed from Chicago to Washington D.C. with Eco-Skies Alliance participants and government partners on board, demonstrating the safety and performance of SAF.

United Airlines Ventures

United has a long history of investing to support the technologies that can decarbonize air travel. In 2015, we invested $30 million – the largest SAF investment by an airline at the time – in Fulcrum BioEnergy, a startup working to commercialize the production of SAF from household trash. In 2021, United created a formal investment vehicle by launching United Airlines Ventures (UAV), a corporate venture capital arm that seeks promising sustainable aviation technologies and innovation to usher in the future of air travel. As of March 2023, UAV is the only airline venture capital fund launched to specifically target technologies and startups that complement a transition to net zero aviation.

To scale the production of SAF, UAV has invested in several producers, feedstock developers, and development projects. Most recently, United announced a $5 million investment in carbon capture technology company, Svante, to potentially unlock CO2 as a feedstock for SAF. This comes after the company’s investment in Viridos, a developer of SAF feedstock via genetically engineered algae. Earlier in 2023, United formed a joint venture, Blue Blade Energy ("Blue Blade"), with Tallgrass Energy and Green Plains Inc. to commercialize SAF technology using ethanol as the feedstock. If the technology is successful, United has entered into an offtake agreement with Blue Blade to receive up to 135 million gallons of SAF annually for up to 2.7 billion gallons in total—our largest offtake agreement. In 2022, UAV invested in NEXT Renewables, a company which—at full production—could produce up to 50,000 barrels per day of renewable fuels, including SAF. UAV also previously invested in Cemvita Factory, a biotech company seeking to commercialize the production of SAF through a revolutionary new process using CO2 and synthetic microbes, and Dimensional Energy, a company whose technology converts CO2 and water into usable ingredients for the Fischer-Tropsch process.

In late 2022, UAV invested in Natron Energy, a battery manufacturer whose sodium-ion batteries have potential to further enable our ground operations’ electrification. UAV also has investments in alternate propulsion, with Heart Aerospace, a company developing 30-seat electric aircraft, and ZeroAvia, a company manufacturing hydrogen fuel cell engines to retrofit on regional aircraft.

Sustainable Flight Fund

In February of 2023, United Airlines launched the Sustainable Flight Fund, a first-of-its-kind investment vehicle focused specifically on SAF technologies. Starting with more than $100 million in dedicated capital, with launch partners—Air Canada, Boeing, JP Morgan Chase, GE Aviation, and Honeywell—to support and invest in startups working on SAF research and development, production, and technology. Through the Fund, the anchor partners and potentially additional corporate participants will invest alongside United in SAF technology and production startups identified by UAV.

The purpose of the Sustainable Flight Fund is to accelerate SAF supply through collective capital. This fund targets technologies that solve for key pain points in current SAF production, and with that unlock access to future SAF production—often times at a scale much larger than volumes that can be purchased through current day production technologies.

As another feature of the Sustainable Flight Fund’s launch, United provided its customers the opportunity to get involved and directly contribute $1.00 to $7.00 to supplement United’s investment in the Fund when booking travel on the website and app. This initiative bolsters the demand signal for SAF, while allowing our customers to have a direct role in helping us achieve our sustainability goals. Notably, within the first ten days of the program launch, over 4,200 customers had elected to contribute.


  1. The data presented herein reflecting United’s 2022 GHG emissions footprint has been internally validated by United Airlines Internal Audit Department and is awaiting final third-party verification. United obtains this third-party verification of our GHG emissions on an annual basis. ERM Certification and Verification Services (ERM CVS, a wholly owned subsidiary of the ERM Group, a global market leader in sustainability services) conducts our emissions verification and provides an ISO 14064-3 limited assurance on our GHG emissions for reporting. Upon receipt of said verification, this report will be amended to reflect the updated data set.
  2. Municipal solid waste
  3. Processes that use heat and specific catalysts to remove impurities and synthetic jet fuel. Examples include pyrolysis and gasification and Fischer-Tropsch
  4. Source:
  5. Source:
  6. The Roadmap and forecasts depicted therein are based on United’s current or selected assumptions on relevant matters as of the publication date of this report, including currently available optimistic and medium- to best-case scenario net zero scenarios and pathways, as set forth in further detail below. The Roadmap should be read with the context of each lever’s further description below, each of which is incorporated within the Roadmap. The Roadmap assumes emissions from Scopes 1, 2, and Scope 3, Category 4, but is not reflective of United’s current GHG accounting methods as it does not explicitly show Scope 3, Category 3 emissions. The Roadmap does not include estimates of non-CO2 effects of aviation though it does include CH4 and N2O. These forecasts were not third-party validated and may change over time to reflect updated projections and assumptions and future conditions, events, and circumstances. United reserves the right to make additions, deletions, or other revisions to this roadmap in the future, including changes to the relative weighting of various levers or the addition/deletion of certain levers, as it deems appropriate. The roadmap is based on various aviation net zero scenarios, including the ATAG Waypoint 2050 Report, MPP Making Net Zero Aviation Possible Report, ICCT Vision 2050 Report, FAA Aviation Climate Action Plan, and ICAO LTAG Report.
  7. Figure derived from data inclusive of well-to-wake emissions, as well as all Scope 1 and Scope 2 emissions, as well as Scope 3 categories 3,4,7,14 and 15 emissions.
  8. 50% reduction in carbon intensity by 2035 compared to 2019 baseline
  9. The BAU scenario incorporates both United’s network plan estimates as well as current estimates of potential future growth based on US GDP growth estimates from the Congressional Budget Office’s Long-Term Budget Outlook and Boeing
  10. Not reflective of specific UAV portfolio companies, instead reflective of technologies generally accepted in industry and academic literature to be available in the stated timeframe. Excludes emissions from technologies included in UAV portfolio that would provide services outside of United’s current service offerings such as supersonic travel and eVTOLs.
  11. Does not include estimates of specific aircraft technology currently under development, but rather relies on estimates of both fleetwide intragenerational improvements assuming a combination of technologies and intergenerational improvements to aircraft efficiency consistent with historic leaps in aircraft efficiency. A selection of potential and illustrative technologies are included in ATAG’s Waypoint 2050 report
  12. Source: 2021 United States Aviation Climate Action Plan (
  13. Analysis assumes future improvement of current operations between the theoretical best and worst cases with additional adoption of fuel efficiency opportunities not in place today.
  14. Based on internal United estimates of future SAF uptake representative of the volumes of SAF required to reach United’s 2035 goal. Projected global SAF volumes based on an average of the ATAG Waypoint 2050 and ICAO LTAG Report scenarios with medium attainability. In 2050, the combustion of SAF will still result in GHG emissions from the aircraft engine. These levers assume available GHG accounting methodologies will recognize upstream emissions reductions from SAF thus netting out any emissions from combusting SAF when considering SAF emissions on a lifecycle basis.
  15. Sources: Making-Net-Zero-Aviation-possible.pdf (, w2050_v2021_27sept_full.pdf (