Dunne replaces Saad Hammad, who leaves the low-cost carrier to join private equity firm Gores Group as managing director.
Hammad was responsible for the appointment of Publicis to its £20m pan-European advertising and direct marketing accounts in October 2008.
Dunne left AOL in June following a restructure of the company by new global chief executive Tim Armstrong.
Last week, easyJet revealed plans to cut flights out of London Luton Airport by 20%, and close its base at East Midlands Airport altogether.