Charlotte Harper, the marketing director at Travelocity, said: "We have enjoyed a long and successful relationship with St Luke's, but the time is right for a change. We now have different requirements from an agency and we are in talks with several shops in advance of a formal pitch."
It is not yet clear how many agencies will be invited for a final pitch.
The planning account, which is held by Klondike, in which St Luke's owns a small stake, and the buying account, held by Universal McCann, will not be reviewed.
St Luke's has held the Travelocity account since the dotcom boom took off in 1999. Its most recent work for the brand was a cinema, press and radio campaign. The agency will continue to work with Travelocity until the autumn, with further advertising due to launch next month.
Its latest cinema spot, "stewards", featured a series of clips of camp male flight attendants talking about the routes they fly, with each description containing large doses of sexual innuendo such as "harder servicing".
The ads aimed to position Travelocity as the travel web site that offers the most choice for consumers.
In February, St Luke's was the runner-up in the Aerial Awards for its "stopover" spot for Travelocity.