The Global Aerospace Centre for Icing and Environmental Research Inc. (GLACIER) facility is located in Thompson, Manitoba, Canada. This facility provides icing certification tests for large gas turbine engines, as well as performance, endurance and other gas turbine engine qualification testing.This globally unique outdoor engine test and certification facility was officially opened back in 2010. The prime purpose of this facility is for icing certification of aero gas turbines. As a generic engine test facility, it includes the infrastructure and test systems necessary for the installation of both current and future gas turbine engines.The GLACIER facility completed its commissioning in the winter of 2010/2011, and has now experienced five years of full icing seasons. Rolls-Royce and Pratt and Whitney have both successfully performed certification and engineering icing testing with 5 engines completing their icing certification. Behind the successes there have been some aspects that could have gone better. Some could be considered an inevitable part of engine testing in the real world, but there have been some learning experiences that can be usefully shared with the wider community.This paper aims to examine and publicize the lessons learnt from these first five years of operation, including how the facility hardware has performed, what availability has been achieved, what we have learnt about the icing spray system and how we plan to develop the facility for the future, including the possibility of incorporating ice crystal and mixed phase testing, as well as SLD (Supercooled Large Droplet) testing.