(WHTM) — After the nation realized foreign terrorists had just attacked the homeland for the first time the country became eerily quiet. The FAA ordered all planes to land and stay grounded. But then, three fighter jets appeared over Three Mile Island.

“We immediately directed the nation’s nuclear plants to go to the highest level of security at the time,” Diane Screnci of the Nuclear Regulatory Commission said.

CONTINUED COVERAGE: Each day leading up to September 11, we’ll share stories of the impact the event had and continues to have on our lives. Read more.

Since the partial meltdown in 1979, the Midstate nuclear plant has been infamous. The nuclear regulatory commission knew an attack on the plant could be another psychological blow.

I asked, “What would have happened had one of those planes nose-dived into TMI that day?” “We did analysis over time and determined that there could be a radiological release but there were plans in place to deal with that,” Screnci said.

“There was a conjecture that Flight 93 was heading toward Three Mile Island,” Eric Epstein of TMI Alert said. The watchdog group had been pushing the plant to increase security when the planes hit the World Trade Center and the Pentagon. To this day, plane, train, and boat traffic all come close to the plant. “TMI is located closer to an airport than any other nuclear power plant in the country,” Epstein said.

Harrisburg’s airport was there first. The plant was built later. “What’s ironic is that you cannot fly over Disneyland but you can fly over Three Mile Island which gives you a sense of where the country’s priorities are,” Epstein said.

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“Nuclear plants are the most hardened commercial building in the United States,” Ralph DeSantis said. On 9/11 DeSantis was communications director for the region’s nuclear plants. “This plant and all nuclear plants have containment buildings in the United States that are designed to withstand the impact of a large jetliner without reaching the building,” DeSantis said.

DeSantis says there would be no release of radiation. Still, after the attack, $30 million worth of security upgrades were made and more staff were hired. But TMI Alert says those precautions have now gone by the wayside. “If you go to TMI now, you’ll see the north and south gates are wide open, no guards, we’re sending out what I think, is the wrong signal,” Epstein said.

Because the nuclear industry has become unprofitable, the plant is being decommissioned and decontaminated. But that could take as many as 90 years. “And right now you have a serious threat. This is one of the last nuclear power plants in the country that has radioactive waste stored in the spent fuel pools,” Epstein said.

Ralph Desantis says it’s important to know that nuclear power plants are the most robust commercial facilities in our country, and he says heavily armed, professional security guards are at these buildings 24/7. Terrorists, he says, usually go after easier targets.