Under the deal, WPP has first refusal on all marketing, PR, advertising and other work with Ford.
She becomes the first woman to head up one of the 'big 5' PR firms. Rob Flaherty to continue as chairman.
The airline could appoint one agency globally or multiple to cover different geographies.
Bell Pottinger has become only the second agency in the past ten years to be excluded from the PRCA, following a ruling on a complaint about its infamous work in South Africa.