A middle aged man and a 75-year-old woman have been arrested on suspicion of criminal damage over a security breach at Shannon Airport.
Belfast IRA woman Mairead Farrell's brother Niall Farrell and Margaretta Darcy, were arrested at their homes in Galway city and county.
The pair were first arrested last month during a protest in Shannon against US drone strikes in Pakistan.
An investigation was launched after two people carrying anti-war banners and placards breached a perimeter security fence on October 7.
Shannon has been used as a transit route for the US war effort in Afghanistan.
A Garda spokesman confirmed a man in his 50s and woman in her 70s were arrested at 9.30am and taken into custody at Millstreet station in Galway.
The pair are being held under section four of the Criminal Justice Act and can be detained for 24 hours.
Mr Farrell's sister was shot dead by the SAS in Gibraltar in 1988.