Internet giant Google launched a flight search tool on Tuesday in a potential challenge to online travel services.

The feature, rolling out over the course of the day, will initially be limited to some U.S. cities and show results for round-trip economy flights only.

Flight search is a feature that helps you explore air travel options for a number of cities, and plan your trip with just a few clicks of the mouse

Google said it will add more cities and options later. Flight Search shows flight options for a selected destination organized by departure time and date, airport, price or airline.

A “Flights” link will appear on the left-hand side of the page when a Google search user types in a query for flight information. Flight Search can also be directly accessed through google.com/flights.