MELVILLE, N.Y. — The explosion and flash shattered the summer twilight, and debris and fuel rained down through the darkness and set our ocean on fire.

This was July 17, 1996, when TWA Flight 800, 16 minutes out of Kennedy Airport and bound for Paris, went down 10 miles south of Long Island. Aboard were 230 passengers and crew. As the terse journalistic phrase goes, there were no survivors.

Thursday evening, families of those who perished, along with politicians and rescue workers from that night 12 years ago, were expected to gather at the Flight 800 Memorial at Smith Point County Park on Long Island.

At the ocean's edge, they were to remember those they lost, but their presence also testifies to the enduring power this singular event holds on Long Island.

At least some of Flight 800's resonance stems from the horror that greeted the sturdy fleet of would-be rescuers who steamed to the crash scene. Amid the flames and wreckage bobbed bodies, along with personal effects, including children's toys.

And back onshore, uncertainty gripped the region. What happened?

At the time, the nation considered the possibility that the crash had been the result of terrorism or an accidental strike by our own armed forces. People said they saw a missile rise from the ocean's surface and hit the jet. Such theories abounded that summer. Anxiety churned the air. People debated it all.

Although such notions still circulate, they have mostly been discredited with years of investigative work by the government.

Six years after the crash, a black granite memorial to Flight 800 was dedicated at Smith Point.

A few years after that, the Federal Aviation Administration announced new safety requirements for commercial aircraft flying in the U.S. These focused at first on wiring issues that helped spark the Flight 800 fire. Airline industry officials fought the new rules.

Wednesday, the Federal Aviation Administration announced it would require new, anti-explosive devices to be installed in center fuel tanks of thousands of aircraft.

It is perhaps the final major piece in the regulatory legacy of TWA Flight 800. The aircraft makers and airlines will be busy for years to ensure they are in compliance.

For the rest of us, the memories linger of a warm twilight and an interrupting flash somewhere over the water, and, when we learned what happened, a sense that our island could not quite be the same ever again.

John Valenti writes for Newsday. Distributed by the Los Angeles Times-Washington Post News Service