Bus from Belfast to Dublin airport

there are a few options on getting from Northern Ireland to Dublin airport
the first is the Translink Ulsterbus goldliner service from Grand Central station , Translink are the public transport operator in Northern Ireland and operate all buses and trains in Northern Ireland including cross border routes into Ireland across the land border, you can take the express X2 or X1 service run by them to Dublin airport, there are also two private operators on the route dublin express and air coach they depart from Upper Queen street, however from September under a deal they have struck with Translink they will be allowed to use Grand Central station

Yes, I would book in advance and I would go with the Dublin Express as opposed to Air Coach. The Dublin Express has more room and a bathroom.

I think it’s possible to buy tickets on the spot, if seats are available. When we took the bus between Dublin and Belfast in June 2024 it was pretty full both in directions. I’m thinking it’s possible for them to sell out. I would say to book online as soon as your plans are firm (whether that’s months ahead, or hours ahead), especially if you’re connecting to a flight at DUB airport. In our case we used Aircoach one way and Dublin Express for the return to Dublin. Both were fine and on time, but the Dublin Express bus seemed a bit nicer/newer.

As said above, and in numerous previous threads, Translink are the third operator on the route.
They were the original operator, and are still the cheapest by a good margin when booked ahead.
They have also always run from Belfast bus station, not random street side stops.
It is a mystery why so many on this forum choose to ignore their existence.

We just returned from Ireland and used TransLink round trip when visiting Belfast for a couple of days. We prebooked and were glad we did, as there was a scramble to get on board from Dublin airport. Anyone with a ticket was boarded first. With a pre book, it was only £17.50 RT for 2. Both trips were on time

I literally just took the Aircoach direct bus from Belfast to Dublin airport this past Wed. I bought the tix a month in advance. The only prob is they just moved their pick up spot from the Upper Queen st to the Grand Central train station but our tickets didn't say that. So when we got to the spot on Upper Queen, it was the local Metro bus drivers there. Thankfully we had plenty of time to rush the few blocks to get to the train station.
From there, the bus pick up was right on time and we got to the airport in just around 2 hours.

Thanks to all for recommendations. We did take Dublin express and it worked out easily. Luckily we knew they switched to grand central station from upper queen street. Thanks to all

heads up aircoach and dublin express services from Belfast to Dublin arrive into and depart from *grand central station * this is the main bus and railway station in Belfast, the other services to dublin airport by bus are operatored by Translink (who are the public transport provider in Northern Ireland) who operate train and bus services in Northern Ireland including cross border train and bus services to dublin and dublin airport, and own and operate Grand Central station and they kindly allow Air coach and Dublin express to operate out of the Bus part of the station this is a new arrangement that has been negotiated between Translink NI and Air Coach and Dublin Express