United Airlines’ Sustainable Flight Fund has announced a strategic investment in Heirloom, a California-based startup pioneering direct air capture (DAC) technology, marking a significant push to curb aviation’s carbon footprint.
The fund, a coalition of aviation and corporate leaders, also secured rights to purchase up to 500,000 tons of carbon dioxide removal (CDR) from Heirloom—a move aimed at scaling sustainable aviation fuel (SAF) production or storing emissions underground.
Heirloom’s innovation harnesses limestone, a naturally abundant mineral, to absorb CO₂ from the atmosphere. By accelerating limestone’s natural carbon-capturing properties, the company claims its method could become one of the most cost-effective pathways for large-scale carbon removal. This partnership marks United’s third investment in carbon capture ventures but its first dedicated to DAC, a technology that extracts CO₂ directly from ambient air rather than at emission sources like factories or power plants.
“Carbon capture is a critical tool for decarbonizing industries that lack immediate alternatives,” said Andrew Chang, head of United Airlines Ventures. “Heirloom’s scalable model aligns with our goal to invest in solutions that are both environmentally impactful and commercially viable.”
The aviation sector, responsible for roughly 2-3% of global CO₂ emissions, faces steep challenges in achieving net-zero targets by 2050. While sustainable aviation fuels and hydrogen-powered flights are part of the equation, experts argue DAC could play a pivotal role in offsetting emissions that are harder to eliminate. Heirloom CEO Shashank Samala emphasized the dual potential of DAC: “It not only reduces the carbon footprint of aviation fuel but also removes residual emissions, creating a realistic path to net-zero air travel.”
The Sustainable Flight Fund, launched in 2023 with over $200 million in commitments, includes backers such as Air Canada, Boeing, Google, and Honeywell. Its cross-industry approach reflects growing pressure on airlines to collaborate with tech and finance sectors to meet climate goals.
Critics, however, caution that DAC remains energy-intensive and costly compared to traditional carbon reduction strategies like reforestation. While Heirloom has not disclosed pricing, industry estimates suggest DAC costs range from $600 to $1,000 per ton of CO₂ removed—far higher than many nature-based solutions. Advocates counter that technological advancements and government incentives, such as U.S. tax credits under the Inflation Reduction Act, could drive prices down significantly by 2030.
United’s bet on Heirloom underscores a broader industry shift: airlines are increasingly hedging their climate strategies with carbon removal technologies, even as SAF production lags behind demand. With global air travel rebounding post-pandemic, the urgency to balance growth with emissions cuts has never been sharper. For now, the success of such investments hinges on whether DAC can transition from promising prototype to mainstream solution—and whether travelers and regulators are willing to foot the bill.
