Previously, Declan was CEO of London City Airport, a role which he held since 2012, and prior to that he was CEO of Dublin Airports Authority for seven years. He is currently a non-executive board member of The Royal Schiphol Group and TCR International N.V. He has broad experience in transport and business and has served as President of the World Association of Airports, Airports Council International (ACI); Deputy Chair of the Airport Operators Association (UK); and as Director of London First; Allied Irish Banks Ltd, and The Dublin Theatre Festival.

Appointed as non-executive member of the board from 19 November 2018, Declan started his role as ORR Chair on 1 January 2019.