When visiting Dublin again after 8 years with my family of four we purchased tickets with return from Dublin airport. The trip to city centre on thursday 18 April went excellent. When returning on Monday 22 April to airport from Dublin city centre, the busses first came with delay and all of them refused to let us onboard since we have not an "online reservation" and they expected to be full, hence not allowing us to join. After getting refused twice we jumped on Dublin bus no 16 that took us to airport without any problems and to a significant lower price (well... very expensive since we have a return ticket that is not used). We managed to arrive at boarding just before they closed the airplane doors. Never Aircoach again, next time we do Dublin Bus!