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By Robert Rapier on Nov 30, 2009 with no responses

Three Gallons Per Mile

Often when I am flying, I think about the amount of fuel that the airplane is burning. Then when I am off the plane, I usually forget about it. I have heard mixed opinions on the overall efficiency of airline travel versus automobile travel, but just never got around to investigating the matter myself.

Earlier this month I was on a flight from Hawaii to Dallas, and the pilot started talking about some of the plane’s statistics. Paraphrasing, he said: “Today we will be cruising at an altitude of 38,000 feet in this Boeing 757. This aircraft burns about 3 gallons of fuel per mile, and is carrying 243 passengers.” I thought “Hey, I better write that down and figure out later on what my share of the fuel was.”

The distance from Honolulu to Dallas is 3,800 miles. Thus, per the pilot the fuel consumption should have been approximately 11,400 gallons. In the Wiki link to the Boeing 757 article above, the Boeing 757 specifications state that the plane only holds 11,500 gallons, so I think it is likely that we were really getting a bit better than 1/3rd of a mile per gallon.

Divided by 243 passengers, my share of the fuel is 47 gallons. This much fuel carried me 3,800 miles, so my pro-rated fuel economy is 81 miles per gallon. In all likelihood, as I said it was probably a bit better than that since I doubt we were landing in Dallas with only 100 gallons of fuel in reserve.

Of course it is important to note that while the fuel economy looks pretty good, the miles traveled are very high relative to automotive transportation. I generally travel less than 5,000 miles per year with my car, so if I drive a car that gets 25 miles per gallon it would only take about 16,000 miles on an airplane to equate to an entire year’s consumption in my car. I estimate that I have probably flown 300,000 miles in the past two years (which was one of the main reasons I left my last job).

One other item of interest to me is my prorated cost for fuel. At $2.00/gallon, $94 of my ticket price goes toward purchasing fuel, and every $1.00 increase boosts my pro-rated fuel cost by $47 for that Honolulu to Dallas trip. That’s actually surprising to me, as I would have guessed that it would have been more.

But that’s not really what hurts the airlines when fuel prices go up. I think what usually happens is that fewer people fly, and instead of pro-rating my share of the fuel across 243 passengers it may be prorated across only 180 passengers. In that case my share of the fuel rises to almost $200 when jet fuel rises to $3.00 per gallon – and thus a $1.00/gal rise in the cost of fuel translates into a several hundred dollar per ticket price increase.