It was just before 9 p.m. on a rainy Sunday in December 1963 when a ball of flames appeared in the stormy sky over Elkton, Md., a rural town about 40 miles south of Philadelphia International Airport. Residents who heard a sound like thunder watched from living-room windows and cars as fiery pieces of metal rained down over a highway and cornfield at the edge of town.

The lightning bolt that struck Pan American World Airways Flight 214 that night as it circled in a holding pattern near Philadelphia sent flames tearing through the aircraft, causing it to disintegrate as it fell. All 81 people aboard were killed, more than half of them from Philadelphia and other parts of Pennsylvania.

This weekend, relatives of the victims and those who recall the crash will gather in Elkton to mark the 50-year anniversary of the crash.

For many in the Philadelphia area, Dec. 8 was the day they lost someone they loved.

"It was just such a sudden shock," said Richard Sherman, who grew up in Philadelphia and whose father was killed in the crash. "It was a nightmare . . . something that to this day is still hard to talk about."

Sherman is one of more than 100 people who are expected to go to Elkton on Sunday for a memorial that will involve sharing stories and paying tribute to the men who ran to the scene that night and tried to help.

Mike Dixon of the Historical Society of Cecil County said the crash traumatized the community. Volunteer firefighters never expected to be combing through plane wreckage. Hours after the crash, a first-responder suffered a heart attack and died.

The flight, using a Boeing 707, originated in Puerto Rico and carried 24 people from Philadelphia, 19 from elsewhere in Pennsylvania, and nine from New Jersey. After making a stop in Baltimore, it continued north, where it hit a storm system, Dixon said. The debris scattered over a four-mile area, some of which was farmland that has since been developed into townhouses.

Before the crash, some experts believed planes could not be hit by lightning. The bolt that struck Flight 214 ignited fuel vapors in a reserve tank, according to an investigation by the Civil Aeronautics Board, causing a wing to catch fire and explode. That finding led the Federal Aviation Authority to recommend that lightning-discharge wicks be installed on all commercial jets.

Bob Hefele, now 56, was tucked into bed in Allentown on the night of the crash. His parents were supposed to return that night from a trip they had taken to Puerto Rico with friends, and he remembers hearing his grandmother breaking down in tears as she heard the news. Soon, aunts and uncles began arriving at the home where Hefele and his three older siblings lived.

"We were lucky because we had a lot of family nearby who were willing to raise us and take care of us," Hefele said. "But it was awful. You never really get over it."

Sherman, whose father had gone to Puerto Rico on a golf trip with friends, said the trip was the first he could remember his father taking without the rest of the family. After his father's death, he said, his mother went back to work as a dental hygienist so she could support him and his two brothers. Those brothers will also join him in Elkton this weekend.

"We hope it will be therapeutic to be with others who remember this," Sherman said.