That’s not to say that jetliners will disappear overnight, but rather that the cheap flights we’ve seen in the past will soon be fading memories. In a few years jet service will be available only to the wealthy, or to the government and military.

Sir Richard Branson of Virgin Atlantic says he wants to use biofuels to power his fleet of 747’s and Airbuses. There are still some bugs to be worked out in terms of basic chemistry, but it might be possible in principle—if only we could make enough biodiesel or ethanol without further driving up food prices and wrecking the soil. Even then it would be very costly fuel.

Are there other options for powered flight?

Hydrogen could be burned in jet engines, but doing so would require a complete redesign of our commercial aircraft fleet, and H2 would be expensive to make—unless the growing trend toward more costly electricity (as we phase out depleting, polluting coal and increasingly scarce natural gas) can somehow be reversed.

Last year I was invited to give the keynote address at the world’s first Electric Aircraft Symposium. NASA and Boeing sent representatives, but all told there were only about 20 in attendance. The planes being discussed were ultralight two-seaters: that’s the limit of current or foreseeable battery technology. These might come in handy in a future where they are the only option for emergency air travel (blimps need depleting helium or explosive hydrogen). But forget about 300-seat planes running on solar or wind power, ferrying middle-class vacationers to Bali or Venice.

There are good reasons to cut down on air travel voluntarily: flying not only swells our personal carbon emissions but spews CO2 and other pollutants into the stratosphere, where they do the most damage. However, the worsening scarcity of the stuff we use for making jet fuel takes the discussion out of the realm of optional moral action and into that of economic necessity and personal adaptation.

I fly to educate both general audiences and policy makers about fossil fuel depletion; in fact, I’m writing this article aboard a plane en route from Boston to San Francisco. I wince at my carbon footprint, but console myself with the hope that my message helps thousands of others to change their consumption patterns. This inner conflict is about to be resolved: the decline of affordable air travel is forcing me to rethink my work. I’m already starting to do much more by video teleconference, much less by jet.

Those who live far from family will be more than inconvenienced, as will the hundreds of thousands who work for the airline industry directly or indirectly, or the millions who depend on tourism or airfreight for an income. These folks will have few options: teleconferencing can accomplish only so much.

Our species’ historically brief fling with flight has been fun, educational, and enriching on many levels to those fortunate enough to benefit from it. Saying goodbye will be difficult. But maybe as we do we can say hello to greater involvement in our local communities.