Airports Council International (ACI) World has issued a white paper urging regulators and the aviation industry to modernise the global airport slot allocation system. The association says a framework created more than 50 years ago is no longer suited to aviation growth, leaving scarce airport capacity inefficiently distributed and creating barriers to competition, connectivity and socio-economic development. The number of the world's most congested, slot-restricted airports has increased by over 25% in the past decade, while global passenger traffic is projected to nearly double by the mid-2040s. ACI World says regulators should work with the industry before the capacity crunch worsens. Justin Erbacci, Director General of ACI World, said the industry is operating in 2026 under rules resembling a 1970s system, limiting its ability to respond to passenger demand, offer competitive fares and build resilient networks. ACI represents 811 members operating more than 2,200 airports in over 160 countries as of January 2026.