Yesterday Boeing announced that one of its pilots recently took to the air in an airplane powered by hydrogen fuel cells. This marks the first time a manned aircraft running on fuel cells has ever successfully completed a flight, though robotic drones have done so in the past.

It's a name only a government agency could love: the Future, Fast, Flexible, Fractionated, Free-Flying Spacecraft United by Information eXchange. Could DARPA possibly come up with a more tortured title for System F6?

Last summer, more than 1,000 environmentalists in the U.K. staged a weeklong protest in a "Climate Camp" at Heathrow Airport, where about 70 people were arrested. Their immediate purpose was to block a planned expansion of Heathrow, but the protests highlighted a growing complaint in Europe—that the ride to global-warming catastrophe is being fueled not only by coal-fired power plants and SUVs, but also by the ever-rising number of commercial jets. Now governments are starting to listen.

When a Concorde jet on its way from Paris to New York crashed on July 25, 2000, killing all 109 people aboard and four on the ground, the event was not simply a tragedy -- it seemed a metaphor for the sorry state of supersonic air travel.