Aer Lingus is among three airlines facing legal action over allegedly breaching consumer law in their handling of passenger delays.
Britain's Civil Aviation Authority says Aer Lingus, Wizz Air and Jet 2 failed to make the necessary changes to their policy, as requested by the regulator.
Jet 2 have responded to the allegations - saying they are paying compensation to passengers for disruption to journeys.
Meanwhile, in a statement, a spokesperson for Aer Lingus says "Aer Lingus’ procedures, relating to the provision of information to customers affected by operational disruption, are fully compliant with all the relevant regulations".
It goes on to say they have "provided a number of documents to the CAA in recent months to substantiate this point and continue to engage with the CAA to address their concerns".
