A leaked concept note on the Commission Implementing Act for CORSIA credit quality criteria narrows the pool of credits European air carriers could use to comply with CORSIA. Especially in Phase I, for which compliance is due already in January 2028, virtually none of the current (already small) CORSIA-eligible supply would be available to European air carriers. For Phase II, the note opens for credits from the Kyoto Protocol’s CDM successor, Paris Agreement Crediting Mechanism (PACM – also known as Article 6.4 Mechanism). The concept note does not represent an official Commission position, but if implemented, it would reduce demand for current CORSIA-eligible credits from European carriers and also put them at a competitive disadvantage to their non-European counterparts when it comes to CORSIA compliance in 2028 and beyond.