Your primary gateway into Ireland is via Belfast, through Belfast International Airport, or via Dublin, through Aerfort Bhaile Atha Cliath, or Dublin Airport, which is 10 km north of Dublin City.
One of the leading no-frills, budget-fare airlines offering cheap flights to both Belfast or Dublin is easyJet. If you’re looking for really cheap Ireland flights, you can fly via Ryanair, Europe’s largest no-frills, budget-fare airline, which is also based in Dublin.
Other U.K.-based low-cost airlines that have Belfast flights are bmibaby and Jet2.com; European low-cost carriers servicing routes to Belfast include Wizz Air (Hungary-based), and Zoom Airlines (Canada-based).
Another way to fly is SkyEurope, a small, budget-fare airline that offers cheap flights to Dublin and (mainly) Eastern European cities, particularly the Czech Republic.
Other low-cost airlines flying routes to Dublin are Clickair (Spain-based), Germanwings (Germany-based), and Flyglobespan (Edinburgh-based).