I've flown over 200,000 miles for work, and I've seen efficient airlines and wasteful ones. Some airlines now fly with single-engine taxiing and lighter seats, but I also see empty business-class seats on every flight. Could the industry cut fuel use significantly just by optimizing seating and routes, or do we need radical changes like synthetic fuels? I'm curious—when you book a flight, do you ever choose the more efficient airline?