Roadmap to net zero by 2050

To achieve our climate targets, we are unabashedly focused on in-sector emissions reductions and driving meaningful progress towards our goal of net zero by 2050 without the use of voluntary carbon offsets.

Our GHG emissions and carbon footprint in 20231

A pie chart that represents our greenhouse gas emissions footprint.

  • The green pie slice correlates to our Direct (Scope 1) emissions, which equal 74%
  • The light green pie slice correlates to our Other indirect (Scope 3) emissions—outside of scopes, which equal 26%
  • The dark green pie slice correlates to our Indirect (Scope 2) emissions, which equal less then 1%

Tracking our progress toward net zero

Our reporting methodology aligns with corporate best practices for GHG accounting protocols, including updates in guidance from the Greenhouse Gas Protocol and SBTi. This supports greater transparency and comparability of the GHG emissions resulting from conventional jet fuel and SAF.

Our 2023 GHG footprint incorporates GHG emissions from conventional jet fuel production, referred to as “well-to-tank” (WTT) emissions. This methodology captures 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 line item.

How we measure our GHG emissions

This graphic represents our well-to-wake GHG emissions footprint, which captures the full lifecycle emissions of conventional jet fuel usage. Our well-to-tank (fuel production) is at 20% and represented in light green, with our tank-to-wake (fuel used by aircraft) at 80% and represented in green.

In May 2023, SBTi approved our 2035 near-term carbon emissions reduction target. This independent external validation demonstrates that our near-term target is science-based and aligns with a trajectory that seeks to limit global warming to well below 2.0°C above pre-industrial levels. Our SBTi-approved target is our ambition to reduce Scope 1, 2 and well-to-wake jet fuel GHG emissions, including emissions from conventional jet fuel production and United’s emissions from regional partner airlines. We are committed to reducing these emissions 50% per revenue ton kilometer (RTK) by 2035 from a 2019 base year. 2, 3

Emissions intensity over time

This is a graph that represents emissions intensity vs. carbon intensity and absolute emissions vs. gross GHG emissions. The black line on the graph represents our gross GHG emissions from 2019 to 2023, which has gone up in recent years due to growth, while the green line is our emissions intensity which is going lower as the years progress.

Although our overall, absolute emissions have increased in 2023 and are expected to increase in the near future due to growth, our carbon intensity has decreased in part due to our use of newer, more energy-efficient planes and increased load factors as demand for travel has increased. Our current expectation for meeting our near-term emissions reduction target is detailed in our Decarbonization Roadmap.

Decarbonization Roadmap4

This illustrative roadmap models a potential pathway for United to achieve net zero emissions by 2050, based on a number of assumptions and hypothetical scenarios. This year, we have updated our roadmap to include the upstream indirect emissions from jet fuel production, i.e., “well-to-wake” emissions accounting. Moving to the more comprehensive “well-to-wake” accounting incorporates the full lifecycle of conventional jet fuel production. Aside from our 2050 net zero target, this roadmap does not reflect United’s climate targets or commitments. Instead, it is a potential forecast for achieving net zero based on a society-wide energy transition scenario, and might change as the underlying scenarios and assumptions evolve.

We seek to reduce our conventional fuel consumption on a per seat basis through advancements in next generation aircraft technology, aircraft fuel efficiency improvements via fleet renewal, more efficient operations and alternate propulsion technologies. We also aim to replace our conventional jet fuel with sustainable aviation fuel (SAF) over time.

United Decarbonization Roadmap

This is a graph that represents emissions intensity vs. carbon intensity and absolute emissions vs. gross GHG emissions. The black line on the graph represents our gross GHG emissions from 2019 to 2023, which has gone up in recent years due to growth, while the green line is our emissions intensity which is going lower as the years progress.

Emit less by using less

Reduce our fossil jet fuel consumption and emissions with more efficient aircraft, operational efficiencies and investments in lower carbon alternate propulsion technologies.

This is a wedge chart that shows what United’s total GHG emissions would be in 2050 if we continued with business as usual and did nothing to address our carbon footprint. Each color represents a different type of action, or lever, we can take to reduce our carbon footprint. These levers are represented with dark blue for Future AC Technology, blue for Fleet Renewal, purple for Ops Efficiency, yellow for Alternate Propulsion, green for Advanced SAF Technologies, light green for Today’s Commercial SAF and dark green for Next Generation SAF. We also represent with a black line what our emissions will look like if we continue with business as usual, as well as a blue dashed line to show our target emissions. All summed up, these levers are expected to reduce our footprint significantly to net zero emissions in 2050.

  • Future AC technology: 13.3%
  • Fleet renewal: 20.8%
  • Ops efficiency: 5.4%
  • Alternate propulsion: 3.6%
  • Today's commercial SAF: 18.1%
  • 2nd generation SAF: 29.8%
  • 3rd generation SAF: 9.8%

Advancements in aircraft design and engine technology often supports improvements in fuel efficiency, which means fewer GHG emissions. Our roadmap forecasts the potential benefits of several advancements such as new engines, open rotors, more aerodynamic airframe designs and future generation aircraft models that are currently in the design phase.5 Our estimate is that by 2050, future generation aircraft could be up to 30% more fuel efficient than today’s commercial fleet.6 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 to 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 800 narrowbody and widebody aircraft, with options to increase that number to nearly 1,000 narrowbody and widebody aircraft, with an expected 20% improved fuel efficiency per seat, compared to older planes. United took delivery of 85 new planes in 2023 and plans to take delivery of 66 new planes in 2024. These new, more efficient aircraft, combined with fuel efficiency measures on seat density, result in 21% of our forecasted emissions reductions by 2050.

Operational measures that enable more efficient and direct flight can also reduce our GHG emissions. 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 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 5% from BAU in 2050.7

As we look forward to 2050, United anticipates that zero-carbon aircraft technologies like battery, electric or hydrogen propulsion may be adopted for shorter-haul distance flights. Through the use of renewable power to charge aircraft batteries as well as the electrolyzers used to make green hydrogen for hydrogen propulsion, we believe these aircraft have the potential to support low-carbon operations for regional flights. We forecast 4% of our 2050 reductions from BAU will be attributed to the adoption of these alternative propulsion aircraft.

Adopt more sustainable alternatives

Support scaling, commercializing and adopting SAF within aviation through demand signals, investment and procurement.

This is a separated-out portion of the Decarbonization Roadmap that represents how through supporting scaling, commercializing and adopting SAF within aviation, we’ll be lowering our emissions over time. These levers are represented in green for Advanced SAF Technologies, light green for Today’s Commercial SAF and dark green for Next Generation SAF.

  • Today's commercial SAF: 18.1%
  • 2nd generation SAF: 29.8%
  • 3rd generation SAF: 9.8%

Sustainable Aviation Fuel (SAF)8

Large scale-up and adoption of SAF is a critical enabler toward achieving our climate targets. United is both purchasing SAF today and investing in future supply of SAF. The SAF levers represented in the Decarbonization Roadmap reflect our expectation of the transition of SAF technology pathways over time:

Currently, 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 compared to conventional jet fuel (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, recognizing this SAF pathway will play a prominent role in decarbonizing our emissions (contributing 18% of the forecasted reduction in 2050).

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 alcohols to fuel. These feedstock sources, often viewed as waste materials, are much more widely available today and could, if SAF production from them is commercialized in the future, result in greater lifecycle GHG reductions than current commercially available SAF.

SAF pathways are forecasted to continue to emerge as we approach the final decade of our roadmap, and as the broader economy transitions to scale up cleaner energy technologies.9 We believe technologies not commercially available today, including carbon removals, have the potential to produce carbon negative SAF on a lifecycle basis in the future. 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 2050. 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.

What is SAF?

Sustainable Aviation Fuel is an alternative to conventional jet fuel that can reduce GHG emissions up to 85% on a lifecycle basis. 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.

This graphic showcases the differences between the extracting, refining and consuming of conventional jet fuel, vs. the processing, refining and consuming of sustainable aviation fuel.

Conventional jet fuel process consists of:

  • 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 process consists of:

  • Process feedstock: Renewable materials are collected as SAF feedstock
  • Refine: Feedstock is converted to fuel through processes that optimize for carbon reduction as much as possible
  • Consume: Finished product is tested to prove identical to jet fuel and used to fly aircraft

SAF’s potential to scale is due to its ‘drop-in’ readiness, which means it can be used in current operations with existing infrastructure, with no changes to fuel systems or aircraft engines required.

United’s current portfolio of SAF suppliers use feedstock like residual fats, used cooking oils and greases, which are otherwise considered waste, to make SAF. Notably, SAF is produced in several ways, such as using hydro processed esters, fatty acids (HEFA) and Fischer-Tropsch synthesis. The feedstocks, refined via these processes, reduce emissions from SAF on a lifecycle basis compared to conventional jet fuel.

United sources SAF from producers that have been issued certificates by independent, recognized sustainability certification schemes, which consider a broad range of requirements prior to certifying that SAF meets their sustainability criteria.

Leading in a hard-to-abate industry

United is taking action to transition the industry with a focus on sustainable aviation fuels (SAF)

A timeline of our efforts and goals from 2016 to 2050 to adopt, scale, expand and invest in SAF to achieve the long-term goal of being net zero by 2050.

  • 2016: Early adopter—1st airline globally to use SAF in ongoing operations
  • 2021: Scaling both supply and demand—Launching two first-of-their-kind programs: Eco-Skies Alliance, partnering with corporations to buy more SAF, and United Airline Ventures (UAV) to advance innovations in sustainability
  • 2022: Expansion of SAF usage—First international SAF expansion into Amsterdam Airport by a U.S. airline
  • 2023: Investing to accelerate SAF innovation—Introduced a sustainable financing collaboration, the UAV Sustainable Flight Fund to help scale SAF solutions
  • 2035: United’s near-term target—Validated by the SBTI1, United’s near-term target is to reduce carbon intensity 50% by 2035 from a 2019 baseline
  • 2050: United’s 2050 ambition: net zero—Achieve net zero GHGs without use of voluntary carbon offsets

Scaling SAF

SAF today is in limited supply. The International Air Transport Association (IATA) estimates that in 2023, nearly 160 million gallons (600 million liters) of SAF were produced globally,10 while the entire aviation industry used more than nearly 80 billion gallons (300 billion liters) of conventional jet fuel.11 Meaning, the entire global supply of SAF represents less than 1% of the world’s fuel usage. As of December 2023, the total volume of SAF used in United’s operations remained less than 0.1% of our total aviation fuel usage. These challenges have informed our strategy of investing in SAF producers and technology to help scale the SAF market and unlock future supply.

This is a vertical bar chart that represents in green the volume in gallons that we have been scaling our SAF usage each year from 2019 to 2023.

  • 2019: 1,153,652 gallons
  • 2020: 624,731 gallons
  • 2021: 600,625 gallons
  • 2022: 2,869,636 gallons
  • 2023: 7,112,587 gallons

* Neat SAF refers to the unblended, Sustainable Aviation Fuel procured by United. This SAF volume then needs to be blended with Conventional Jet Fuel in order to be used in our operations.

United recognizes that the current SAF volumes available in the market today are insufficient for the decarbonization of air travel, underscoring the need for collaboration involving both private and public sectors, including policymakers, cross-industry partners, low-carbon fuel producers/suppliers, employees and customers. United is participating in multiple efforts to address current challenges, including investing in technology that could help scale the SAF market, exploring potential SAF production sources and advocating for policies that encourage the use of SAF.

Creative financing for sustainable flight

Eco-Skies Alliance

United launched the Eco-Skies Alliance in 2021 to foster co-investment support for SAF, addressing the “green premium”, or price difference between SAF and conventional fuel. Through this first-of-its-kind program, United partners with our sustainability-minded corporate customers to reduce their GHG emissions from travel with United by funding the green premium. Since the program’s launch, the Eco-Skies Alliance has grown to include nearly 40 corporate customers, supporting the use of over 11,000,000 gallons of SAF and reducing our collective environmental impact by over 115,000 mT CO2e, WTW. That is the equivalent to the emissions of the energy usage of over 12,600 homes in a year, highlighting the positive impact of our collaborative efforts.

United’s Eco-Skies Alliance continued to grow in 2023 and doubled the number of SAF delivery locations from 2022, bringing a blend of SAF and conventional jet fuel to United flights operated out of London Heathrow Airport and San Francisco International Airport. This comes after United already voluntarily integrated an SAF blend into its operations at Amsterdam Schiphol Airport and Los Angeles International Airport. Thanks to the Eco-Skies Alliance, United more than doubled its SAF usage in 2023 compared to 2022, despite global SAF shortages.


The Eco-Skies Alliance is supported by a system called “book and claim”. This enables United to “book” physical SAF being used, displacing a corresponding volume of conventional jet fuel, and delivered to a United operational location. The customer travel emission reductions associated with the use of that SAF are then “claimed” in a different operational segment, uniquely allocated to where the Eco-Skies Alliance customer is flying. United then creates “SAF Certificates”, which outline the delivery location, volume and GHG emissions benefits of the SAF consumed in our operations and provided to Eco-Skies Alliance customers, allowing them to recognize these travel emission reductions. The “book and claim” model provides our customers the flexibility to support the usage of SAF without having to physically be on the flights containing SAF. Book and claim has also been used by SAF producers, sustainability certification schemes, and various cross-sector organizations geared toward scaling sustainable travel solutions.


This graphic represents in colored bars how our Eco-Skies Alliance works.

  • The dark green section states that we are: Actively partnering with our corporate customers
  • The blue section states that we are: Procuring SAF on a global scale
  • The green section states that we are: Embedding SAF into our operations at all airports instead of jet fuel
  • The light blue section states that: Customer interest and demand for SAF supports growth in the industry

United Airlines Ventures

United has a long history of innovation, and in 2021, this extended to sustainability with the launch of United Airlines Ventures (UAV), a corporate venture capital arm that invests in promising sustainable aviation technologies and innovation to usher in the future of air travel. UAV includes three dedicated investment verticals: technology, aerospace (including alternative propulsion aircraft and vertical takeoff and landing) and a decarbonization vertical, focusing on startups and solutions to help aviation and United reach its climate goals.

Sustainable Flight Fund

In February 2023, UAV expanded its decarbonization vertical by launching a fund with third party, limited partner (LP) capital investments: the Sustainable Flight Fund. This first-of-its-kind investment vehicle, was created to accelerate SAF supply through collective capital by targeting investments in technologies that solve key pain points in current SAF production.

Given the supply constraints in the SAF market today, and foreseen value chain constraints in medium-term scaling, the Sustainable Flight Fund has maximized the capital UAV is able to deploy via the addition of LPs from all sectors: fuel technologists, aircraft original equipment manufacturers, financial institutions, integrated energy, consulting and more. The fund is sized at 22 corporate partners and over $200 million in capital raised, with the aim of investment in technologies to scale the available supply of SAF.

The United Airlines Ventures logo and Sustainable Flight Fund is centered in a sectioned circle that is dark blue, blue, and light blue, with offshoots from those colors. This graphic represents how this fund has helped us expand our SAF usage through partnership in blue, an innovation portfolio in dark blue, and co-investment in light blue.

2023 Investment highlights:

  • JANUARY

    United forms Blue Blade Energy with joint venture (JV) partners Tallgrass Energy and Green Plains Inc. to commercialize SAF technology using ethanol as a feedstock

  • FEBRUARY

    The Sustainable Flight Fund launched with $100M in committed capital from United and its inaugural corporate partners Air Canada, Boeing, GE, JP Morgan Chase and Honeywell

  • MARCH

    The Sustainable Flight Fund invested in Svante, a startup developing materials and technology as part of the carbon capture value chain

    The Sustainable Flight Fund also invested in Viridos, a synthetic biology company developing an algae biofuel through bioengineered microalgae that is optimized for increased oil yield

  • JULY

    UAV invests in Electric Power Systems, a startup producing battery technology with potential uses for a broad suite of aerospace applications

  • OCTOBER

    The Sustainable Flight Fund invested in Electric Hydrogen (EH2), a company specializing in the production of low-cost electrolyzers, which can produce green hydrogen. Hydrogen is a key input into the SAF process - including a potential feedstock for 3rd generation SAF

  • NOVEMBER

    Sustainable Flight Fund also invested in Banyu Carbon; a carbon capture company focused on removing CO2 from the ocean (known as direct ocean capture). CO2 can be a valuable, unlimited resource as a future feedstock for SAF, represented as 3rd generation SAF in United's Decarbonization Roadmap

Footnotes

  1. The data presented herein reflecting United’s 2023 GHG emissions footprint has been internally validated by United Airlines Internal Audit Department and externally verified by our third-party verification party ERM. 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.
  2. The target boundary includes biogenic emissions and removals from bioenergy feedstocks.
  3. Non-CO2e effects which may also contribute to aviation induced warming are not included in this target. United Airlines Inc. commits to report publicly on its collaboration with stakeholders to improve understanding of opportunities to mitigate the non-CO2e impacts of aviation annually over its target timeframe.
  4. 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, Categories 3 and 4, reflective of United’s current GHG accounting methods. 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. The BAU scenario incorporates both United’s network plan estimates as well as current estimates of potential future growth based on U.S. GDP growth estimates from the Congressional Budget Office’s Long-Term Budget Outlook and Boeing. 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.
  5. 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, beginning page 40 here: w2050_v2021_27sept_full.pdf (aviationbenefits.org)
  6. Source: 2021 United States Aviation Climate Action Plan (faa.gov) p. 7.
  7. 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.
  8. 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.
  9. Making-Net-Zero-Aviation-possible.pdf (missionpossiblepartnership.org), (sources: Making-Net-Zero-Aviation-possible.pdf (missionpossiblepartnership.org), w2050_v2021_27sept_full.pdf (aviationbenefits.org)
  10. Net zero 2050: sustainable aviation fuels
  11. Boosting SAF production | Biofuels International Magazine (biofuels-news.com)