Last April, we dissected the worlds most advanced fighter jet, the F-35B Lightning II, in the pages of our annual How It Works issue. Now military contractor Lockheed Martin is firing up the jets 40,000-pound-thrust engine (the most powerful ever built for a fighter jet) in preparation for flight tests. The jet can soar at supersonic speeds (1,000 mph) and deflect radar signals, but by the end of the month, pilots are expected to show off its most highly anticipated feature: the ability to stop mid-flight and touch down virtually anywhere.

I've noticed that the F-35 Joint Strike Fighter and the F-22 Raptor, both of which are in development by Lockheed Martin, look strikingly similar. What's the difference between the two?

Marc Tidalgo

New York, N.Y.

As satellites grow bigger and more powerful, so must the rockets that carry them into orbit. A new generation is emerging-not only are they more muscular, but they're also efficient and environmentally friendly. In the battle for the world's launchpads, here's how the contenders stack up.
Vehicle: Ariane 5Maker: Arianespace (France)First launch: June 1996First payload: Cluster scientific satellites (destroyed)Capacity (in Chevy Suburbans): 3.8More info: www.arianespace.com

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.