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Comment by carleverett | Hacker News Reader

Not good. A Cessna 172 cruises at 140 mph and burns 8.5 gph of 100LL fuel, the equivalent of 16.5 mpg, and this is at cruise speed, not accounting for taxi, run-up, and flying the pattern during a normal flight.

Not to mention we're still burning lead in most propeller aircraft as well.

Fortunately this isn't a very popular way of getting around.

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It’s interesting that it’s not insanely bad. I assumed it would be maybe 2-10X worse but it’s in a similar ballpark.

Would a full on private jet be way worse?

Would these planes carry a fair few people than a car? If so what’s it like taking passenger numbers into account?

I guess super-rich folk probably would be happy to fly just themselves in a big private jet and also be travelling waaaay further than they ever would in a car so it’s probably a silly comparison anyway

There's actually a huge range in private planes. This M600 plane does about 7 mpg, 250 knots at 45 gph. A typical light jet might do 400 knots at 125 gph (3 mpg). But a light jet cannot not fly nonstop to a different continent. For these trips, a large business jet might do 450 knots at 300 gph (1.5 mpg), but only the very super rich can actually afford these. Even most celebrities will be flying the airlines for long international trips.

Thanks for the calculations! It’s weird how a more advance technology like a jet can be so successful yet an order of magnitude less economical. Usually it’s the reverse. But when you’re rich it’s time that’s money

The short answer is that higher speeds come at a steep price. The relationship between velocity and the power required to overcome drag at that velocity is cubic, so that large business jet requires on the order of 50x more power to fly at 450 kts than it would flying at 120 kts, like the little Cessna might.

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