Composition 2

And it gets worse from there. Despite recent fluctuations, a growing number of economists are bracing for oil to hit or surpass $200 per barrel in a few years, and most industry analysts agree with Douglas Runte, of RBS Greenwich Capital, who told The Wall Street Journal in June, "Many airline business models cease to work at $135-a-barrel oil prices." After all, most airlines barely figured out how to be profitable in a world of low fuel costs. Jeff Rubin, chief economist of Canadian investment bank CIBC World Markets, has predicted that gasoline will hit $7 per gallon by 2010, forcing some 10 million cars in the United States off the road. If that happens, he told me, "You're going to see an even bigger exit in the airline industry."

As if one plague wasn't enough, the threat of climate change could mean further doom for airlines. In Great Britain, green groups are lobbying hard in favor of aviation fuel taxes and against a proposed third runway at Heathrow Airport, wewhile activist groups, like one called Plane Stupid, have taken to unfurling banners from atop Westminster Palace and elsewhere with slogans like WE FLY, WE DIE. They argue that, at a time when greenhouse gases are pushing global temperature to perilous levels, flying--one of the most energy-intensive forms of travel around--is a luxury the planet simply can't afford. (While aviation currently accounts for just 3 percent of man-made carbondioxide emissions, it's one of the fastest-growing sources, and the true climate impact of flight is around 2.7 times that of carbon dioxide alone, thanks to the added warming effects of nitrogen-oxide emissions and jet contrails.)

"That's the real deal," says Bill Swelbar, a research engineer at MIT's International Center for Air Transportation. "When you look at some of the taxes and fees being discussed in Europe, we might as well bankrupt our industry today." John Whitelegg, a transportation expert at York University's Stockholm Environment Institute, estimates that requiring airlines to pay the full environmental costs of flight could raise fares as much as five-fold.

One far-reaching scenario, however, was put forward by Anthony Perl and Richard Gilbert, two Canadian transportation experts who, in their new book Transport Revolutions, envision a world in which rising oil prices have reduced domestic flying in the United States roughly 40 percent by 2025--even assuming that airlines improve fuel efficiency by about 50 percent. In such a scenario, the United States could go from having nearly 400 primary airports down to 50 or so; instead of dozens of flights each day between New York and San Francisco carrying 200 people apiece, there might be only a handful carrying 800 or more in new extra-jumbo jets.

Maybe the gloomy futurists have a point after all, and mass aviation could be coming to an end. No longer would air travel be like the Internet or television--a cheap technology available to virtually anyone, shaping our world in countless little ways. If that happened, the result would mean more than just the end of easy weekend jaunts to Bermuda or annual Christmas visits home. It could mean major shifts in the economy, changes in immigration patterns across the world, and perhaps even a remapping of the planet as we know it.