Careplane lets travelers compare the environmental impact of itinerary choices when searching for flights on their favorite travel sites, allowing them to make flight purchases based on sustainability in addition to cost and convenience.The app is a free browser plug-in for Safari, Firefox, and Chrome that springs into action whenever you visit sites like Kayak and Orbitz, and calculates a high-resolution carbon footprint for each itinerary option in your flight search results. Not surprisingly, equally-priced flight options often have very different environmental impacts due to aircraft characteristics, the number of passengers on board, and other factors. Nutrition labeling and organic certification have brought sweeping changes to the food industry by empowering informed consumer choices -- Careplane is part of the effort to do the same for the air travel industry. Careplane is powered by greenhouse gas data from the EPA's US Greenhouse Gas Inventory, flight census data from the BTS, fuel data from the EIA, and standards-certified energy and emissions models from Brighter Planet. Installing Careplane in takes just a couple clicks. To get started, go to http://careplane.org and click on "Install."