While most airlines are skimping on basics like food and pillows, one carrier is going in a different direction. Virgin America is selling environmentally conscious passengers the chance to fly guilt free. It's the first domestic airline to sell carbon-offset credits in-flight. Passengers concerned about their carbon footprint on a cross-country flight can buy the credits from their seatback screens. Virgin America directs the money to one of two green projects in California. So far, 1 percent of the airline's passengers have used the service.