My airline fuel use

Undoubtedly to the disdain of those who seek to minimize energy use and, in particular, energy use that involves travel via the burning of fossil fuels, I do a significant amount of airline travel. And, beginning in August of 2017, I added fuel burn (by asking the flight crew, who is invariably happy to entertain my questions), distance traveled, and number of passengers on each flight to my log. I calculate such things as passenger miles per gallon, joules of fossil fuel energy used per passenger, and a variety of other pieces of data.

For the “big numbers,” I’ve flown 27,068 miles on 25 “legs.” Over these miles, I’ve been responsible for 383 gallons of jet A being burned, for a mileage of 70.7 m.p.g. As my patient readers likely would infer, despite my having exchanged my Lexus CT 200h in which I achieved over 50 m.p.g. for a Jeep Grand Cherokee SRT that achieves about 16.5 m.p.g., I still obsessively log my driving fuel burn. In the time that I’ve traveled the 27,000 miles in airliners, I’ve driven 12,573 miles and burned 758 gallons of gasoline for a mileage of 16.46 m.p.g. I very rarely have a passenger in my car. I'd estimate that, of the 12,573 miles, I've had a single passenger for something like 750 miles which results in a passenger mileage of 17.6 m.p.g. Miles driven with more than one passenger were negligible. Had I traveled those same miles in the CT 200h, I'd have burned about 241 gallons of fuel.

What can I make of this? 68.3% of my miles traveled have been in airliners (ignoring when I've been in the road vehicles of friends and associates) but only 33.6% of the volume of fossil fuels burned have been in those airliners. Again, had I still been driving the Lexus CT 200h, the figures would be 68.3% (of course) and 61.4%.

The fact of the matter is that modern airliners are amazingly efficient. If I drove my Jeep with three passengers, I'd still not exceed the fuel economy of the airliner, though the same four people in the Lexus would far exceed that fuel economy. But I'm not aware of anyone who carries a full car load of people any for any significant fraction of their driving.

The most common engines on my flights are the CFM56-7B series (the dash 7B24 variant was the culprit on Southwest flight 1380 that suffered a fan blade rupture resulting in the death of a passenger). The dash 7B24 variant produces a maximum thrust of 24,200 lbf (pounds force) and the dash 7B26 produces 26,300 lbf, though these thrust levels are only used during takeoff and early climb. A typical number in cruise is more like 5,800 lbf. Giving that a little thought, it's pretty startling that a force of 11,600 pounds is all that's needed to push a vehicle with a weight on the order of 150,000 pounds through the air at 530 m.p.h.

There's no doubt that my travels, both now in the Jeep and multiple times per year in the "big silver bird" are contributing more than my fair share of carbon emissions. If I use very rough figures, the 39,641 miles that I've traveled since August of 2017 annualize to the emission of something like 15 tons (Imperial short tons that is) per year of carbon dioxide attributable to my travel with about 36% of those emissions due to airline travel.