PBN provides the basis for future global navigation capability as defined in the ICAO Global Air Navigation Plan (GANP) and defined in the Airspace System Block Upgrade programme (ASBU), with operators keen to utilise the technology available on their aircraft fleets. The highly accurate navigation capabilities of modern aircraft, utilising both ground and space-based navigational aids provides an opportunity to address the capacity and efficiency issues of the airspace while making best use of the aircraft navigation capabilities and operators investment. At the same time, greater considerations must be given to the environmental impact that aviation has on local communities. The UK airspace air traffic management structures require modernisation to accommodate the increasing demand for commercial air travel while safely accommodating increasing demands for airspace access from a wide variety of other users. PBN impacts both the high-level airways and the lower level arrival and departure routes into and out of airports and instrument approach procedures.PBN is being adopted world-wide and States are expected to modernise airspace through International, Regional and State level initiatives, including regulations.The requirements for PBN, in terms of accuracy, integrity and continuity of service that airborne navigation systems must demonstrate, is set out in international standards – ICAO Doc 9613. In parallel, the UK navigation infrastructure can also be optimised to take advantage of the lateral navigation accuracy from Global Navigation Satellite Systems (GNSS) while retaining adequate conventional ground-based navigation aids to ensure both resilience and contingency measures. Key to achieving this is through the application of Performance-based Navigation (PBN). One of the major aims of the Airspace Modernisation Strategy (AMS) is to optimise future airspace designs to take account of modern aircraft performance and functional capabilities and make them more efficient – saving time and fuel and reducing emissions.