Let’s do some maths !
Dependent upon the number of passengers onboard, a typical B737-300 ( the low cost airline aeronautical chariot of choice ) uses the following amounts of fuel:
2670 kg / flight hour when full of passengers
2600 kg / flight hour when 75% full of passengers
2380 kg / flight hour with no passengers
Now as I’m going to compare the fuel used when flying, to that used in a car full with four people on the same journey, I’m going to assume that my B737 aircraft is also full with 148 passengers onboard, i.e. both car and aircraft are operating at their max capacity & efficiency.
So we know that when our B737 is full of passengers, the weight of fuel burnt in one hour on an average sector: 2670 Kg
Working that back into volume ( using a Kerosene specific gravity of 0.8 ) it equates to: 2670 / 0.8 = 3338 Litres ( * 0.2204 ) = 736 Imperial gallons.
Now in one hour a typical B737 will cover, say, 500 statute miles.
So how many miles to the gallon is that ? 500 / 736 = 0.68 miles to the gallon
Ouch ! That sounds awful, doesn’t it ? – but hold on, this is a machine that’s moving 148 passengers.
If we divide the volume of fuel used in one hour by the number of pax on board : 736 / 148 = 4.97 gallons of fuel per passenger per flight hour.
So miles per gallon per passenger ( 500 / 4.97 ) = 100
Or in other words, for each of the 148 passengers onboard our B737, it takes one gallon of fuel to move that person 100 statute miles.
Putting that in car terms, i.e. chunking together four people at a time, we can see that it equates to an airborne fuel efficiency of 25 miles per gallon - uhm, now does that figure sound familiar to car drivers ? – albeit that this is achieved at 500 MPH…..
Just try getting that kind of efficiency, when four-up, in your car at even 100 mph !