The Orbitz site spent approximately $13 million in measured media 2001, according to Taylor Nelson Sofres' CMR.
A spokeswoman for the client said there was an "amicable" parting with TBWA/Chiat/Day but declined to comment on the status of the relationship with Fusion.
"At this point our needs have shifted and we are evaluating alternatives to a full-service agency," she said.
Five airlines -- American, Continental, Delta, Northwest and United -- were founders of the business.
An AdAge.com e-mail alert sent out earlier today inaccurately reported that the move involved TBWA/Chiat/Day's San Francisco office. It did not.