International aviation emissions within the European Economic Area fall under the EU Emissions Trading System. Aviation was included in the EU ETS by Directive 2008/101/EC of 19 November 2008, amending Directive 2003/87/EC. The original 2008 legislation was designed to cover CO2 emissions from all flights departing from, arriving at, or within the EEA. However, due to international opposition, the scope was temporarily reduced by Regulation (EU) No 421/2014 to cover only intra-EEA flights (the 'reduced scope' or 'stop the clock' derogation), and this restriction has been repeatedly extended. Following the 2023 revision (Directive (EU) 2023/958), the EU ETS for aviation continues to apply to all intra-EEA flights. The limitation to intra-EEA scope was extended one final time until the start of 2027; by July 2026, the European Commission will assess whether to expand coverage to flights departing the EEA to third countries not participating in ICAO's CORSIA scheme. The aviation ETS cap was initially set at 95% of 2004-2006 average emissions (approximately 221.4 million allowances). Aircraft operators were originally allocated 82% of allowances for free, with 15% auctioned and 3% held as a special reserve for new entrants.