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* Birds of a feather. Getting unmanned aircraft to fly in formation is a challenge that still escapes DARPA scientists, according to Tactical Technology Office program manager Tom Beutner. "Formation flight is an idea we know should work," he says. "We see it even in nature, yet while we routinely use formation flight for tactical advantage, it has never been utilized for the full aerodynamic benefit it offers." Flying in formation allows the aircraft behind the leader to conserve fuel by flying in its slipstream, just like geese do when they fly south for the winter. "Only birds now do this routinely, and they can't explain it to us," he said.

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