AIP contains basic permanent aeronautical information essential to air navigation within the Singapore FIR. It is made up of three parts, namely General (GEN), En-route (ENR) and Aerodromes (AD). The AIP is updated regularly, with AIP AMDT issued once every two months. AIP SUP contains information on temporary changes on air navigation in the Singapore FIR. It supplements the permanent aeronautical information in AIP Singapore. AIC contains explanatory and advisory information on technical/ legislative/administrative matters; and the long-term forecast of major changes in legislation, regulations, procedures or facilities affecting flight safety.