Do I absolutely need a reservation on Aircoach on arrival to Dublin Airport. Never really sure of arrival times. Thanks in advance.
Nope. You can buy tickets just outside the terminal in their booth and get on the next bus. They run frequently.
Or you can pay on the bus if there's a long line at the kiosk.
If you do buy in advance the ticket is valid for 24 hours on any later departure with space, in the event of a flight delay.
You have to dig around a bit on their website to find that.