Out for her morning stroll with her dog in San Clemente a few weeks ago, Barbara Fox panicked when she spotted a plane circling the twin domes of San Onofre Nuclear Generating Station. She rushed home to report the sighting and find out what was going on.

Fox was bounced between the Sheriff's Department, the CHP and the Federal Aviation Administration before she finally got some news she never expected: The no-fly zone placed over the power plant after the Sept. 11 terror attacks was no longer in effect.

"They told me it was probably just a student pilot--don't worry about it," Fox said. Don't worry about it? Fox and her neighbors who live in the shadow of San Onofre are now more concerned than ever.

Living next to a nuclear power plant has always brought its share of apprehensions. But in the wake of Sept. 11, residents have become acutely aware that they live next door to what the U.S. government acknowledges is a potential target for terrorism.

Now, the buzz of a plane flying overhead takes on new meaning.

Some residents are mounting a campaign to improve what they consider lax security in and around the plant. They want more armed guards posted, a ban on international flights within 50 miles of San Onofre and the stationing of Marines in the area.

Aside from an airstrike, one of the residents' biggest worries is access to the plant from nearby San Onofre State Beach, which shares a parking lot with plant employees.

Plant officials insist security is more than adequate, and the Nuclear Regulator Commission said San Onofre is well-prepared.

"They have a strong security program. They have not had any significant issues identified there," said Gail Good, who oversees security inspections at 14 nuclear sites in the western United States for the commission.

The pair of curvy, concrete domes of San Onofre sit about halfway between Los Angeles and San Diego. Built and licensed in the early 1980s, San Onofre was a source of angst long before Sept. 11.

The discovery of seismic faults beneath the plant, and a recent proposal to store an estimated 62,500 gallons of nuclear waste at the site, remain concerns to neighbors.

But the terrorist attacks, in which hijacked jets were flown into the World Trade Center and Pentagon, made residents realize the possibility of a deliberate disaster.

Soon after Sept. 11, officials acknowledged that the power plants were not designed to withstand the impact of a jumbo jet.

Plant officials say security has never been tighter and includes background checks of employees, intruder-alert systems and detectors for explosives and metals.

Military resources from nearby Camp Pendleton are immediately available, said Ray Golden, spokesman for the Southern California Edison plant. For example, he said, any suspicious air traffic can be reported to the Marines, "and they would then use their radar to detect that and take any actions they deem necessary."

Vehicle traffic is allowed only through the main entrance, where guards remain armed with semiautomatic weapons and IDs are thoroughly checked. Huge concrete barriers behind other gates keep trucks or cars from barreling through. High-surveillance cameras keep a close eye on activities around the plant.

Outside, the Coast Guard patrols the waters, where there is a one-mile exclusion zone that may soon be extended to five miles. And the California Highway Patrol and state park rangers remain on the lookout for suspicious activity in the area.

"It's an extremely hard target," Golden said.

But residents believe more can be done. They've proposed that San Onofre limit stockpiling of toxic chemicals or abandon the idea altogether, arguing that such a practice would make San Onofre a more attractive terrorist target.

They are asking Gov. Gray Davis to accept the federal offer of potassium iodide drops as a radiation antidote. They also want the warning and evacuation systems to be improved.

Recently, the NRC released a report that said that although security at San Onofre was generally good, there were two security breaches after Sept. 11.

Longtime San Clemente resident Craig McBride fishes nearly every day from rock piles in front of San Onofre's sea wall and thinks security is adequate.

"It's safe," he said, shortly after hauling in a 2-pound sea bass. "If a terrorist comes, I'll cast my fishing line and hook 'em for you."