Passengers flying to the US face enhanced security measures from today.
US officials say new security measures will apply to all flights into America from abroad.
The security measures include the possibility of travellers being questioned by airline staff before being allowed to board aircraft.
Some airlines have advised customers to arrive at airports earlier than normal.
However, passengers travelling to the United States from Dublin and Shannon may not notice any difference.
Aer Lingus has said that as both Dublin and Shannon airports already have US preclearance in place, many of the measures being implemented are already in place here.