Sustainable fuel sources

While aviation accounts for only 2% of global CO2 emissions, we recognize that climate change is a significant global concern. We’ve improved our fuel efficiency by 45% since 1990, but that’s only the first step.

We recognize the role we play in contributing to climate change and our responsibility in solving it. That’s why we’re embracing the goal of becoming 100% green by reducing our greenhouse gas emissions 100% by 2050. Continuing to invest in sustainable aviation fuel (SAF) sources will be a major part of that.

This investment is not only good for the environment, but also has the potential to guard against future oil price instability while creating clean energy jobs in the communities we serve.

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Our partners

At United, we're excited about the innovation that SAF brings to the airline industry. As a leader in advancing these fuels, we’re actively working with strategic partners to generate SAF capable of reducing our CO2 emissions and providing energy diversification.

In recognition of our work in this area, United was named a “Leading Airline” by the Natural Resources Defense Council (NRDC) for having a strong range of commitments and supply chain implementation.

A timeline of firsts

Over the past decade, United has led the U.S. airline industry in SAF and decarbonization. Here are some of our firsts:

  • 2009: first U.S. airline to fly a SAF test flight
  • 2011: first U.S. airline to fly a SAF passenger flight
  • 2015: largest airline investment in a SAF producer
  • 2016: first airline globally to use SAF on an ongoing basis
  • 2018: first U.S. airline to set a GHG reduction goal
  • 2020: first airline globally to announce plans to invest in carbon capture and sequestration
  • 2021: investments in Alder Fuels to advance SAF, Archer Aviation to scale up urban air mobility, and Heart Aerospace to advance electric-powered regional aircraft; and the first airline flight using 100% SAF
  • Today:
    • We have used more SAF than any other airline globally
    • We hold ~70% of all publicly announced purchase agreements for SAF
    • We are the only airline to commit to carbon neutrality without the use of offsets
    • We are the only airline to have announced a commitment to invest in carbon capture and sequestration

In 2021, United was the first airline in the world to operate a flight powered by 100% drop-in SAF. This particular SAF can provide an estimated 75% reduction in lifecycle CO2 emissions, bringing us one step closer to making 100% green — carbon-neutral-aviation — the norm.

World Energy Fuels

In 2016 United became the first airline globally to fly on SAF on an ongoing, daily basis, supplied to our Los Angeles hub by AltAir Fuels (now World Energy). Using technology from Honeywell UOP, World Energy's refinery in Paramount, California, has been retrofitted into an advanced sustainable fuel facility that converts feedstock, such as agricultural wastes and non-edible natural oils into low-carbon advanced sustainable fuels.

In early 2018, World Energy's fuel obtained sustainability certification from the Roundtable for Sustainable Biomaterials. World Energy's fuel meets the same industry standard as petroleum-based products while reducing greenhouse gas (GHG) emissions by nearly 80%. In addition, the use of waste and residue materials are a crucial part of World Energy’s feedstock mix as their use reduces the pressure on land and natural resources which are pivotal factors in the development of a truly sustainable bioeconomy.

Fulcrum BioEnergy

In addition to our purchase agreement with World Energy, United has invested more than $30 million in California-based sustainable fuel developer Fulcrum BioEnergy. Fulcrum has pioneered technology for converting waste and household trash into low-cost SAF using the Fischer-Tropsch process to realize a greater than 80% reduction in GHG emissions.

We are working with Fulcrum to develop SAF refineries located near our U.S. hubs. When built, United has the right to purchase up to 900 million gallons (~3.4 billion liters) of SAF from Fulcrum, whose first facility finished construction near Reno, Nevada in July 2021; a second is planned in Gary, Indiana.

Our agreement with Fulcrum will reduce our carbon footprint, divert waste from landfills and create new jobs at the Fulcrum facilities located in the communities that support our hubs.

Alder Fuels

In 2021 United committed to investing in and purchasing 1.5 billion gallons of SAF from Alder Fuels. Alder plans to produce SAF from biomass such as forest and crop waste and deliver a carbon-negative fuel, with production to begin in 2025. This purchase agreement, which is one and a half times the size of all other airlines’ announced purchase commitments combined, makes this easily the largest publicly announced SAF agreement in aviation history.


  • Sustainable aviation fuel is a low-carbon alternative to conventional petroleum-based fuel that is derived from renewable sources or waste byproducts. SAF is a ‘drop-in’ fuel, meaning it can be safely used in existing aircraft and airport systems without changes to infrastructure. United’s SAF available today has ~80% lower GHG emissions on a lifecycle basis.

  • Sustainable aviation fuels can benefit the environment by significantly reducing the amount of CO2 emissions produced during the "lifecycle" of that fuel compared to conventional jet fuel. "Lifecycle" refers to all emissions produced during the entire process, from extracting or collecting the feedstock to refining, transporting and using the fuel.

  • Yes, there have been thousands of flights using SAF like that produced by World Energy, including flights using the same Honeywell UOP's Green Jet Fuel™ process. The fuel from World Energy meets the same stringent international fuel certification as conventional jet fuel (ASTM Standard D-1655), and the Federal Aviation Administration has deemed this fuel as acceptable for use on aircraft provided it meets ASTM specifications. Because this fuel is considered a "drop in" fuel, no infrastructure or aircraft engine modifications are necessary. Passengers won't notice any difference when flying on an aircraft using 100% petroleum fuel or one using a SAF blend, as both types meet the same technical and safety requirements.

  • There is currently no way to purchase tickets specifically for a flight powered by SAF. Our long-term goal is to expand the use of cost-competitive, commercial-scale aviation SAF to many other locations. We anticipate that our agreements with World Energy and Fulcrum Bioenergy will bring millions of gallons of SAF to more of the airports that we serve in the years to come.

  • First, you can travel with airlines like United that are working to reduce the carbon intensity of flying by making significant fuel efficiency improvements and by increasing their use of SAF. Corporate customers can partner with United through our Eco-Skies Alliance. This program allows corporate customers the opportunity to pay the additional cost for SAF. This contribution goes beyond traditional carbon offsets and will show there is demand for low emissions fuel solutions. Enroll your company today to participate in our alliance program and reduce your carbon emissions from your United flights.