Aer Lingus is tightening its passenger ID rules for UK-Ireland flights this month.
From February 25, all Irish passengers flying across the Irish Sea will have to produce their passport or passport card.
Due to special rules governing UK-Ireland travel, other forms of identification have been acceptable, such as a driving licence and birth certificate.
Later this month this changes, with Aer Lingus only accepting valid passport documents.
The change is related to a new electronic travel authorisation (ETA) system coming into force in the UK.