In a bid to modernize the U.S. air traffic control system and avert air travel gridlock, the Federal Aviation Administration has formulated a 10-year, $11.5 billion plan to replace today's radar-based system with one built around satellites. The project relies largely on Global Positioning System data, rather than radar, for navigation. The problem is that GPS still isn't accurate or reliable enough for such aviation applications. Now, a system that would allow GPS to provide nearly infallible signals for air traffic use is getting ready for rollout. If the technology passes testing over the next several years, it could help make the FAA's grand vision a reality.

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