With the increasing equipage of Global Navigation Satellite System (GNSS) in commercial air transports, and the growing constellation of GNSS, the future use of Geometric Altitude throughout the flight profile might be possible and will bring added benefits such as reduced vertical separation and complementing trajectory flight paths. Geometric Altitude might be introduced above 15,000 metres because all aircraft able to reach these levels are GNSS equipped, but biggest benefit is seen during approach and departure. IFALPA supports research into a possible future transition from Barometric Altitude to using Geometric Altitude for sub transition level en route, and approach operations.