"The airport impacts hundreds of thousands of residents," Yeager said, "and I'm excited that there's now a way for members of the public to educate themselves about how the airport affects them."

Yeager's project for the airport's website began after he saw a similar function being used by San Francisco International Airport. He wanted something similar for the San Jose airport and in April 2002, he looked at various options with airport staff.

According to Jaime Locquiao, the airport's noise abatement manager, the airport already had a contract with Megadata Corporation, whose subsidiary PASSUR (Passive Secondary Surveillance Radar) has established radar relays throughout the country. The San Jose airport uses a relay setup at Twin Creeks Sports Complex in Sunnyvale, and the location is considered optimal for transmitting information, he said.

The real-time flight tracking function is simply a map of the Bay Area on which airplane graphics move across the screen. Clicking on a plane will display its model, altitude and a tracking ID number, which can be used to learn more details about the flight.

For security reasons, the "real-time" tracking system is delayed eight minutes and the tracking ID function works for only an hour after a plane is selected, according to Marina Dyke, the community liaison for the airport's neighborhood services group.

Willow Glen resident Ralph Steiber, 72, finds the function very useful for tracking loud planes flying over his home.

"I'm always concerned with the noise and why sometimes there's a loud roar at 3 a.m.," Steiber said. "Not too long ago there was a Southwest plane taking off at 2:30 a.m., when there's supposed to be a curfew."

Steiber recalls that shortly after he moved to Willow Glen in 1966 the airlines switched from propeller planes to jet engines, and gradually the Willow Glen area grew noisier.

Steiber, like other residents who use the real-time tracking function, soon became fascinated, not only with flights over their homes but with other flights showing up on the system.

"I play around with it from time to time," Steiber admitted.

That's a comment Yeager has heard from other residents as well.

"It can almost be hypnotizing," Yeager said. "Overall I've received positive responses from those who've used it."

The website function, simply called AirportMonitor, operates on a complex system in which radar from the airport and from the Twin Creeks relay send flight data to PASSUR in New York; from there a server provides the content to AirportMonitor clients like the airports in San Jose, Boston and Los Angeles.

The plane icons in AirportMonitor appear to blink across the screen because the radar makes a 360-degree rotation in 4.6 seconds, constantly refreshing the website with new data, Locquiao said.

Supposedly the radar can pick up any kind of aircraft, including private airplanes and helicopters—"anything with a transponder," Locquiao said. But whatever it is, AirportMonitor will still assign it the generic airplane icon.

The Minneapolis airport was the first airport in the country to make an airplane tracking system available to the public via its website, according to Locquiao.

"But it didn't have any security," he said. "The Federal Aviation Administration found out about it and shut it down after only a week."

The AirportMonitor on the San Jose airport website was launched in December and appears to be staying aloft—legally. It may even affect how many complaints the airport receives.

Dyke said that most users would like the AirportMonitor to enable them to type in their home address so they can check on a plane flying directly overhead, not just in the vicinity, as it does now.

Yeager said that because AirportMonitor tracks planes coming and going from other airports, namely the San Francisco and Oakland airports, there might be low-flying planes from those airports.

"Sometimes the noisy plane flying low was going to the Oakland airport," Yeager said, "so San Jose can't always be blamed for curfew violations."

Locquiao also said that FAA specifications for all aircraft for level flight over populated areas is 1,000 feet. But sometimes it doesn't matter how high these planes fly. "They're just loud," he said.

For more information about the AirportMonitor or to use the system, visit www.sjc.org and click on the Airport Flight Tracking System under the 'What's New' section.