Tensions between Libya and the United States had been mounting for years when, in March 1986, the two sides fired on each other in disputed waters off the Libyan coast. The following month, a bomb went off in a West Berlin disco popular with American servicemen, killing two U.S. soldiers and a Turkish woman and injuring more than 200 others. Having intercepted communications that purportedly implicated Libya’s government in the attack, the United States responded with air strikes. “We believe that this preemptive action … will not only diminish [Libyan leader Muammar al-Qaddafi’s] capacity to export terror, it will provide him with incentives and reasons to alter his criminal behavior,” U.S. President Ronald Reagan said at the time.

Qaddafi, however, had not been scared into submission, prosecutors would later indicate. Instead, his agents in Malta allegedly concocted a bomb made of Semtex, a plastic explosive, and hid it inside a radio-cassette player. They then placed it in a suitcase and sent it unaccompanied on a December 21, 1988, flight to Frankfurt. From there, according to prosecutors, it went to London on the first leg of Pan Am Flight 103. At 6:25 p.m., a Pan Am Boeing 747 took off from London’s Heathrow Airport on the second leg of the journey to New York City. Just minutes after the plane off at 31,000 feet, the bomb detonated near the left wing. Power went out instantly and the plane began breaking apart, sending the crewmembers and passengers, including 35 Syracuse University students returning from a semester abroad, plummeting toward Earth. None survived.

Meanwhile, down below in the small town of Lockerbie, Scotland, residents found themselves directly in the path of falling plane debris. When the fuel-laden wings and a section of the main body crashed into one house, the subsequent explosion created a 155-foot-long crater and sent a fireball shooting up into the sky. One policeman reportedly compared it to the mushroom cloud from a miniature atomic bomb. The couple that owned the house died, as did nine neighbors ranging in age from 10 to 82. Homes up to 75 yards away lost their roofs, and those even further from the blast had their doors and windows shattered. Pieces of the plane came down elsewhere in Lockerbie as well, causing dozens of fires to break out.

Of the 270 victims that day, 189 were American. Their families soon began clamoring for answers, and some even testified before Congress. In May 1990, a presidential commission declared in a scathing report that the U.S. civil aviation security system was “seriously flawed” and had “failed to provide the proper level of protection for the traveling public.” This became obvious a few days later, when the father of a British victim successfully snuck a fake radio-cassette player bomb onto a flight from London to New York and then onto a second flight from New York to Boston. In an attempt to remedy these safety concerns, Congress passed a bill in October 1990 that, among other things, established training standards for airport security personnel and guidelines for notifying passengers of credible terrorist threats. President George H.W. Bush called it a “living memorial to those whose lives were so cruelly cut short.”

Much of the blame for the incident fell on Pan Am, which faced numerous lawsuits and a federal fine of $630,000 for violating security rules. It declared bankruptcy in early 1991 and ceased operating by the end of the year. Around the same time, U.S. and Scottish prosecutors charged Abdel Basset Ali al-Megrahi and Lamen Khalifa Fhimah—both alleged Libyan intelligence agents—with executing the attack. Though Qaddafi at first refused to turn them over, a deal was eventually worked out in which they went on trial in the Netherlands under Scottish law. Only Megrahi was found guilty. He remained incarcerated from 2001 until 2009, when the Scottish authorities, believing he would die within a few months of prostate cancer, released him on compassionate grounds. Proclaiming his innocence to the end, Megrahi finally succumbed to the disease in May 2012.

As for Qaddafi, his regime accepted responsibility—but not guilt—for the attack in 2003 and agreed to pay $10 million to the family of each victim. (Due to a missed deadline, this was later reduced to $8 million.) In return, sanctions were dropped, and the United States restored full diplomatic relations. Just before Qaddafi’s death in 2011, his former justice minister told a Swedish newspaper that the Libyan leader had personally ordered the Lockerbie bombing. Yet even if true, certain facts remain unknown. Some investigators, for instance, reportedly believe that Iran played a role in retaliation for a July 1988 incident in which a U.S. warship mistakenly downed an Iran Air plane with 290 passengers aboard.