We will be arriving on Aer Lingus at the Dublin airport from the US at 5:15 am if on schedule. We may have to check a bag and allow time to pick that up. How long to we need to allow for clearance upon arrival? We have been advised to book a bus to Belfast in advance and wonder how early we could book. Does anyone know whether a reservation can be used on a later bus if the one booked is missed due to flight delay? We have looked at Air Coach and Translink. Are there other optons? Thanks for your feedback.