Kayak became Microsoft’s travel technology partner in 2011, but TripAdvisor today announced a couple of deals with Microsoft as it usurps a bit of Kayak’s turf.

TripAdvisor quietly began powering hotel search on Microsoft’s Bing.com about six weeks ago, replacing Kayak. Kayak still powers Bing.com’s flight search.

Nathan Clapton, TripAdvisor’s vice president of global mobile partnerships, says the deal also includes use of TripAdvisor’s rating and reviews, adding that this “rich content” was one of the drivers of the new relationship.

Clapton is bullish on the benefits of working with Microsoft and its reach in search.

Asked whether TripAdvisor’s new Bing deal means TripAdvisor will eventually power flights for Bing.com, which Kayak currently handles, Clapton said, “we are looking at all opportunities.”

This is TripAdvisor’s first syndication partnership for its relatively new hotel metasearch product.

However, Kayak, it is believed, wasn’t getting a lot of business from hotel search on Bing.com. Several years ago, after Microsoft acquired Farecast and turned it into Bing Travel, Microsoft put some marketing dollars into Bing Travel, but Microsoft’s travel offering eventually got swallowed up into the all-ecompassing Bing, and and the travel offering lost some sizzle.

TripAdvisor also released its first app for Windows 8.1. TripAdvisor integrated Bing Smart Search into the app, and a link to TripAdvisor ratings and reviews appears when travelers use Bing Smart Search to peruse hotels.

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To further complicate the Bing-Kayak and new Bing-TripAdvisor relationships, Kayak still powers flights and hotels for the Bing Travel app.