The media agency, which won the account without a pitch, has been tasked with expanding the airline's 'Uncrowded, uncompromising' marketing campaign.
The account was previously held by Interpublic's US agency, Mullen.
It is understood that the premium airline group is also looking to expand its creative agency roster.
Eos flies the only 757 aircraft configured with 48 'suites', each of which features a horizontal flat-bed.
The airline, which operates 44 flights a week between JFK airport in New York and Stansted, faces competition from start-up carriers such as Zoom and Maxjet Airways.