New security measures come into force today on all US-bound flights, including stricter passenger screening before takeoff.
However, passengers travelling to the United States from Dublin and Shannon may not notice any difference.
The enhanced measures are being introduced to comply with US government requirements designed to avoid an in-cabin ban on laptops.
Airlines say the new measures could also include short security interviews with passengers.
They will affect 325,000 airline passengers on about 2,000 commercial flights arriving daily in the US, on 180 airlines from 280 airports in 105 countries.
The new rules come at the end of a 120-day window for new US safety regulations to be implemented following the lifting of the laptop ban imposed on some Mideast airlines.
Those restrictions were lifted in July, but the Trump administration said it could reimpose measures on a case-by-case basis if airlines and airports did not boost security.
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.
It said pre-clearance flights fully comply with the new requirements and have done so for some time.
Lufthansa Group said on Tuesday the measures would be in place on time and advised that travellers could face short interviews at check-in or at the gate.
Economy passengers on Lufthansa's Swiss airline have been asked to check in at least 90 minutes before departure.
Air France said it would begin the new security interviews today at Paris Orly Airport and a week later, on 2 November, at Charles de Gaulle Airport.
Cathay Pacific Airways Ltd said it would suspend in-town check-in and self bag-drop services for passengers booked on direct flights to the US.
The airline said passengers would also have short security interviews and it has advised travellers to arrive three hours before departure.
Airlines for America, a US trade group, said the changes "are complex security measures" but praised US officials for giving airlines flexibility in meeting the new rules.
Association of Asia Pacific Airlines Director General Andrew Herdman said having a globally coordinated security approach made more sense than having destination-specific requirements.
"This is not a positive," he said of the US measures at an industry conference in Taipei. "It adds complexity."
US authorities in June also increased security around aircraft and in passenger areas, and other places where travellers can be cleared by US officials before they depart.
A Transportation Security Administration (TSA) spokeswoman declined to discuss the specific changes but said "the United States continues to work with our partners to raise the baseline of global aviation security and keep the entire traveling public safe".
The TSA said in July it was imposing new security rules requiring US domestic airline travellers to remove all electronic items larger than mobile phones, such as tablets, e-readers and video game consoles, from carry-on baggage for screening.
