How does my presence on an airplane effect its fuel efficiency?
Fuel efficiency is a characteristic of a given aircraft that is a fixed function of the design, type of engine(s), and similar factors. I fly a single engine airplane with an 85-hp engine that uses about 4 gallons per hour at cruise. That is its fuel efficiency rating. The weight of each passenger has a teeny-tiny effect on the fuel burn for a given flight, but it really is negligible. The typical passenger loading for a wide-body jet on a long haul would be around 60,000-80,000 pounds. So your weight might result in a marginal fuel burn of a couple of pounds per hour, or next to negligible. So don’t feel guilty about the Chocolate Fudge Sunday. Enjoy!