Clune, Aer Rianta's former head of PR, and his deputy McCann announced they would step down after 17 and 38 years with the firm respectively.
The move sparked a review of the firm's in-house PR department, which has seen much of Aer Rianta's corporate PR outsourced to retained agency Fleishman-Hillard Saunders (F-HS).
Incoming PR chief Cussen is now supported by just one staff member, PR manager Siobhan Moore, who remains in charge of media relations, PR and managing F-HS.
'The department's being restructured, but it's still not fully complete,' said Moore, adding further recruitment was dependent on the final outcome of the review.
She said: 'I'm not handling PR alone, our PR consultants F-HS are dealing with a lot of the corporate and policy work.'
Clune is said to be taking early retirement to write a book about his life in Dublin PR - he has been in the industry for 40 years, having formerly worked at Irish airline Aer Lingus.
Aer Rianta formed in 1937, but in recent years has expanded its interests into the retailing, catering, hotel and tourism industries.
The firm recently acquired a chain of hotels, Great Southern Hotels Group, and in 1996 bought a 40 per cent stake in Birmingham International Airport.
It is working on an expansion programme to update its three Irish airports.