Flights

Flights to Shannon - About 20 mins drive from Dromoland Castle

Ryan Air from Gatwick and Stansted https://www.ryanair.com

Aer Lingus from Heathrow www.aerlingus.com

There are also airlines that fly direct Shannon from USA.

Flights to Dublin - About 3.5 hours drive to Dromoland Castle

Many airlines from UK,  the rest of Europe and USA.