This paper has been jointly produced by the European airline associations ERA and A4E to support a targeted 2026 fast-track revision of the ReFuelEU Aviation Regulation. It presents a structured regulatory assessment based on consultations with European member airlines representing network, low-cost, regional and cargo business models. The paper highlights early implementation challenges and how targeted adjustments could make the system work better to enhance proportionality, legal certainty, administrative efficiency and market transparency while fully preserving the Regulation’s environmental ambition.