This thread is being drifted by a strong tangental crosswind!
To get back a little on course/topic, I was intrigued by -
Figures for aircraft and airline fuel consumption are publicly available. Ryanair is a low-cost airline serving mainly European destinations; it seats 189 people in its Boeing 737-800s. Using typical values for sector lengths, fuel consumption and seat occupancy it can be seen that the fuel consumption is marginally greater than 3 litres/100 km/seat - based on typical sector consumption of something over 5 tonnes and a typical sector being something over an hour. This figure will obviously vary depending on sector lengths, cruising altitude, load, winds and air temperature but will remain close to 3 litres/100 km/seat - it will be neither 1.5 litres/100 km/seat nor 6 litres/100 km/seat
Surely aircraft fuel consumption is exponentially greater on take-off? Do the figures above represent cruising consumption or do they take into account take-off as well?
And to get back totally on topic - did I hear correctly that FlyBMI had an average passenger load of 18 per flight? In which case presumably each passenger's carbon footprint would have been enormous!
These figures include take-off consumption. A 737-800 burns roughly 2,400kg per hour in the cruise, so short-haul routes have a higher consumption per sector than long-haul routes for the same aircraft type.
However as TonyK wrote in post 37, consumption is very carefully controlled by the flight ops department and the flight crew. Maximum, or the required, take-off power is used only for two or three minutes or so after which the engines are throttled back for the climb. Generally it takes about 20-25 minutes to reach cruise altitude of 30 to 35,000ft after which the power level is reduced again. To avoid the passengers having ear problems on decent the rate is usually less than about 2,000ft per minute - corresponding to a cabin altitude change rate of around 400 ft/min (for a cruise cabin altitude of 8,000ft). This means that the engines are returned to flight idle for the 20 minutes or so of the descent until the landing pattern is joined. Of course air traffic control may dictate a less than optimum approach so consumption will be higher than the best case would suggest.