CORSIA Takes Flight
The first sectoral growth factor lands — and aviation’s carbon reckoning begins.
After years of theory and policy design, it’s finally real. While 31 October is best known as Halloween, this year it also marked something far more significant for international aviation: ICAO’s long-awaited release of the 2024 sectoral growth factor for CORSIA Phase 1 — 0.15948315.
This figure means that international aviation emissions now sit 15.95 percent above the CORSIA baseline, which is set at 85 percent of 2019 levels. In practical terms, this is the moment when the industry begins to account for its collective carbon liability under the global offsetting scheme.
From Policy to Practice
CORSIA (the Carbon Offsetting and Reduction Scheme for International Aviation) was adopted in 2016 to cap the net growth of aviation emissions from 2020 onward. Yet, for years, it existed largely as a concept. COVID-19 delayed its implementation and altered baseline calculations. Now, with the official growth factor published, the mechanism becomes operational - and airlines will begin to see a tangible cost associated with emissions that exceed the agreed baseline.
This first year of a three-year phase is a turning point for the industry. For the first time, the environmental cost of international flying (at least between participating states and when emissions rise above the baseline) will be recognised within airlines’ balance sheets.
Internalising the Cost of Impact
Philosophically, this is what climate policy is designed to do: internalise the cost of impact. By embedding the price of emissions into operations, it creates both an accountability mechanism and a powerful signal to innovate. For aviation, this means accelerating the shift to cleaner fuels, improved operational efficiency, and ongoing research and development in decarbonisation technologies. Over time, these innovations will define competitive advantage and shape the industry’s transition pathway.
Offsets as a Bridge, Not a Destination
While some see offsets as a stopgap, they remain an essential bridge. CORSIA’s design requires airlines to purchase eligible carbon credits to compensate for emissions above the baseline. These credits finance emission reductions or removals elsewhere - often supporting renewable energy, forest restoration, and community-based resilience projects with significant social and ecological co-benefits.
In doing so, the industry acknowledges its footprint and begins to invest in reductions beyond its own boundaries. This collective effort helps maintain environmental integrity while the sector scales up its own in-sector solutions.
Looking Ahead: Liability and Carbon Supply
Over the three years of Phase 1 (2024–2026), the sectoral growth factor will directly shape airlines’ offsetting obligations. The higher the growth in emissions relative to the baseline, the greater the carbon liability across the industry.
This will place pressure on the supply of offsets, especially as more countries and corporates compete for the same limited pool of verified credits. It underscores the importance of robust governance, transparent standards, and long-term investment in sustainable aviation fuel (SAF) production to complement offsets with genuine in-sector reductions.
More Than Data
0.15948315 might seem like just another number - even one longer than Pi. But behind those digits lies a milestone: the beginning of aviation’s journey to operate within the limits of the planet.
CORSIA Phase 1 is not the finish line. It’s the first real step toward transforming how the world flies, how emissions are valued, and how global cooperation can move from paper to practice.
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