Dublin accounted for over 81% of all flights, while Cork handled almost 8%
Almost 30 million passengers passed through Irish airports in 2015 - an increase of 12.5% over the previous year.
The figures from the Central Statistics Office (CSO) show this is the highest number of passengers handled by Irish airports since 2008 - when 31.3 million passengers travelled through Irish airports.
Passenger numbers increased in all but two airports - Cork and Knock - while Dublin Airport accounted for 83.8% of all air passengers.
The number of departing passengers marginally exceeded those arriving in 2015.
In total, there were 14.83 million arrivals and 14.87 million departures for the main airports.
Almost 232,000 flights were handled by the five main airports in 2015. Dublin accounted for over 81% of all flights (188,771) while Cork handled almost 8% of all flights (17,910).
London-Heathrow, London-Gatwick and London-Stansted were the most popular routes for passengers in Dublin in 2015.
For Cork, the top three routes were London-Heathrow, London-Stansted and Amsterdam.
While in Shannon, the main routes were London-Heathrow, London-Stansted and New York's John F Kennedy - and London-Stansted, London-Luton and Liverpool-John Lennon were the most popular routes to and from Knock.
In 2015, almost nine out out of every 10 passengers (87.7%) on international flights in the five main airports were travelling to or from Europe.
The three most popular countries of origin/destination were the United Kingdom, Spain and the United States - together accounting for 59% of all passengers.
And the main airports handled a total of 149,800 tonnes of freight in 2015, the vast majority (93.2%) of which was international.