Cassandra has moved. Ugo Bardi publishes now on a new site called "The Seneca Effect."

Thursday, March 9, 2017

"Peak Speed" for the World's Airlines




So, it is true: planes fly slower nowadays! The video, above, shows that plane trips are today more than 10% longer than they were in the 1960s and 1970s for the same distance. Airlines, it seems, attained their "peak speed" during those decades.

Clearly, today airlines have optimized the performance of their planes to minimize costs. But they were surely optimizing their business practices also before the peak and, at that time, the results they obtained must have been different. The change took place when they started using the current oil prices for their models and they found that they had to slow down. You see in the chart below what happened to the oil market after 1970. (Brent oil prices, corrected for inflation, source)


It is remarkable how things change. Do you remember the hype of the 1950s and 1960s? The people who opposed the building of supersonic passenger planes were considered to be against humankind's manifest destiny. Speed had to increase because it had always been doing so and technology would have provided us with the means to continue moving faster.

Rising oil prices dealt a death blow to that attitude. The supersonic Concorde was a flying mistake that was built nevertheless (a manifestation of French Grandeur). Fortunately, other weird ideas didn't make it, such as the sub-orbital plane that should have shot passengers from Paris to New York in less than one hour.

If this story tells us something is that, in the fight between technological progress and oil depletion, oil depletion normally wins. Airlines are especially fuel-hungry and they have no alternatives to liquid fuels. So, despite all the best technologies, the only way for them to cope with higher oil prices was to slow down planes, it was as simple as that.

Even slower planes, though, still need liquid fuels that are manufactured from oil. We may go back to propeller planes for even better efficiency, but the problem remains: no oil, no planes, at least not the kind of planes that allow normal people to fly, something that, nowadays, looks like an obvious feature of our life. But, as I said before, things change!


Note added after publication. Out of curiosity, and also as the results of some comments received for this post, I went to look at the rated cruising speed of various passenger planes.  It seems that there is no detectable change in the reported values for similar planes, from the Comet to the Airbus 350. Still, the schedules indicate a slowdown of about 12% in the flight time. In part, I think it is to take into account the crowding of airports but also, in part, there has to be some leeway in how the plane is flown; it can be probably be slowed down, a little, from its rated cruising speed with a small improvement in fuel efficiency.

Who

Ugo Bardi is a member of the Club of Rome, faculty member of the University of Florence, and the author of "Extracted" (Chelsea Green 2014), "The Seneca Effect" (Springer 2017), and Before the Collapse (Springer 2019)