According to the BBC's Future Planet, a cruising Boeing 747 burns through 0.9 gallons (4 liters) of fuel each second. This is equivalent to 3,500 gallons (13,250 liters) of fuel every hour. If a 747 is cruising at its standard cruising speed of around 580 mph (933 km/h), it is covering a mile every 6.2 seconds. Covering a mile requires 5.9 gallons of fuel. As a result, a cruising Boeing 747 can achieve just 0.18 miles per gallon.

However, this is not the full picture, as a 747 carries far more people. SeatGuru writes that Qantas Airways' 747-400 aircraft carry 364 passengers across Business, Premium Economy, and Economy classes. If we extrapolate this number of seats into the mpg that each passenger has, the data shows 65.5 mpg per passenger. According to calculatormpg.co.uk, the baseline for a good car mpg is 50. If a car is carrying two people, then the car is achieving 100 miles per gallon for each person. This suggests that flying on a 747 still uses substantially more fuel than a car carrying multiple people, but less than a car carrying one person.