Ten minus Two?
Your piece on how airborne networks might evolve in the future ("10 Emerging Technologies," May 2005) is a bit behind the times. The ability of aircraft to communicate their identities and positions to other nearby aircraft, and to take evasive action if necessary, has been flying for many years. It's called the Traffic Alert and Collision Avoidance System, or TCAS. It equips planes with receivers that listen to the replies transmitted by other aircraft to interrogations from ground radars. A newer technology, called ADS-B, allows aircraft to broadcast their identities and positions.

None of this, however, has much to do with your article's speculation that these technologies will allow "vastly greater numbers of small planes [to] zip in and out of thousands of small airfields." Those small airplanes fly today with virtually no dependence on air traffic control by the Federal Aviation Administration. These planes have no problem now with crowding of the skies. The problems of crowded skies apply only to the planes that fly under control of the ATC system. The best in new automation won't fix those problems until there are more runways on the ground. It doesn't matter how efficiently we are able to get planes from here to there if there's no concrete to land on.