JECATSD Journal of Environmentally Compatible Air Transport System Discussions JECATSD J. Env. Com. Air Transp. Sys. Discuss. 3053-9285 Göttingen, Germany 10.5194/jecats-2026-4 Efficacy of Scalable Airline-led Contrail Avoidance Sankar Tharun https://orcid.org/0000-0002-0557-0972 1 Dean Thomas 2 Abbott Tristan 2 Blickstein Jill 3 Martín Frías Alejandra 4 Galyen Mark 3 Grenham Rebecca 3 Hodgson Paul https://orcid.org/0000-0002-8650-3906 2 McCloskey Kevin https://orcid.org/0000-0001-9967-4117 1 Pechman Alan 3 Robarge Tyler https://orcid.org/0009-0005-0665-4667 2 Sanekommu Dinesh 1 Sarna Aaron https://orcid.org/0000-0001-8786-5581 1 Sonabend-W Aaron 1 Stettler Marc https://orcid.org/0000-0002-2066-9380 2 5 Zopp Raimund 4 Geraedts Scott https://orcid.org/0009-0001-6496-0153 1 Google Research, 1600 Amphitheatre Pkwy, Mountain View, CA, USA Contrails.org, 4110 Carillon Point, Kirkland, WA, USA American Airlines, 1 Skyview Drive, Fort Worth, TX, USA Flightkeys, Herrengasse 2-4, 1010 Vienna, Austria Imperial College London, Exhibition Road, South Kensington, London, UK 21 04 2026 2026 1 25 Copyright: © 2026 Tharun Sankar et al. 2026 This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/ This article is available from https://jecats.copernicus.org/preprints/jecats-2026-4/ The full text article is available as a PDF file from https://jecats.copernicus.org/preprints/jecats-2026-4/jecats-2026-4.pdf

Contrails account for a large portion of aviation's contribution to anthropogenic climate change. Navigational contrail avoidance is a promising solution to mitigate the warming caused by contrails. Prior trials testing navigational contrail avoidance have relied on bespoke integrations of contrail forecasts into airline operations. Here, we use a randomized control trial to test the feasibility of dispatcher-led contrail avoidance integrated into standard flight planning operations using a workflow that scales to an airline's entire network. We validated the efficacy of this intervention using satellite imagery and an automated flight-contrail attribution algorithm. Using this system, we observed an 11.6 % reduction in contrail formation rate for the 1232 flights marked as eligible for contrail avoidance (intent-to-treat) relative to the flights in the control group (<em>p</em> = 0.011). In the 112 flights that flew contrail avoidance as planned (per-protocol flights), we observed a 62.0 % lower contrail formation rate relative to the flights in the control group (<em>p</em> &lt; 0.001). No statistically significant difference in fuel usage was observed between the two groups.