The system is used at the Schengen Area’s external borders to collect fingerprint data.
Ryanair's calling on the EU Commission to allow member states continued flexibility when it comes to the Entry/Exit System.
The system, which went fully live in April, is used at Schengen Area external borders and registers fingerprints.
Up until now, border officials were able to revert to passport stamps if queues became too long.
From today, that's no longer an option, and, while the checks don't apply to Irish passport holders, travel experts are warning of longer queues at European airports.
Eoghan Corry, Editor of Travel Extra, says current staffing levels are letting the system down:
Fiosrú Examines Death Of Young Man Following Garda Firearms Sting Operation
IFA Calls For Expansion Of Farm Supports In Budget 2027
"Unacceptable And Shocking" - Taoiseach Reacts To HSE Personal Data Breaches
Offaly Hosting Midlands Palliative Care Alliance Launch
Community Meeting Over Midlands Solar Farm Taking Place Tonight
Offaly Playing Host To Fianna Fail Think-In
Gardaí Issue Public Appeal Over Missing Laois Teenager
Historic Offaly Castle Goes On Sale For Nearly €1 Million