Searching for flights on Google just got “greener.”

A new search feature rolled out Wednesday tells users which flights have lower carbon emissions, giving them the ability to choose flights based on carbon emissions just as they would price or the number of layovers.

A basic search for flights will give an estimate of how many kilograms of carbon dioxide the flight will spew from start to finish. Users can prioritize their search by emissions, much like they can by price, if desired.

Flights with emissions below the median get highlighted in green.

Google said the estimates are a combination of data from the European Environmental Agency and flight-specific information it gets from airlines and other providers. That data could include an aircraft’s age, model and configuration, the speed and altitude it flies at and the distance between the flight’s origin and destination.

Some flights may not have estimates because of a lack of data on certain aircraft or other missing information, Google said. The company added that the estimates don’t yet take into account what direction the plane is heading — a potentially significant factor if flying into or with the jet stream, or whether or not the flight is using biofuels or other alternatives.

Using the new tool, the least polluting flights from the Washington, DC, area to Chicago are all United flights using Boeing 737s. The 128 kilograms of carbon dioxide falls 21 percent below the median. An American Airlines flight on another Boeing 737 from San Francisco to New York with a stop in Dallas emits 535 kilograms of carbon dioxide, 9 percent less than the median for that route.