It remains the largest and longest running mass murder investigation in modern times. The 1988 crash of Pan Am 103 in Lockerbie, Scotland, is one of the biggest crashes in aviation history, though questions still remain. Deemed a terrorist attack, the case has been open for 25 years.

On December 21, 1988, shortly after 7 pm, Pan Am Flight 103, a 747 en route from London to New York, exploded at 31,000 feet and fell into the small town of Lockerbie in Scotland. Two hundred and seventy  people — 259 on the plane and 11 on the ground — were killed.

In fact, the families of the victims are still asking why and what happened. A former Libyan intelligence agent, Abdel Basset al-Megrahi, was convicted of planting the bomb, though he has insisted he had nothing to do with the bombing. By 2003, Libya took responsibility for the bombing, agreeing to pay up to $10 million to relatives of each victim.

However, as of March 2013, the FBI is still working to determine exactly who was behind the bombing. Watch Peter’s CBS This Morning report on see the progress and setback of the Pan Am 103 investigation.

For more information on Pan Am 103, check out:

• Peter’s Blog: Remembering Pan Am Flight 103
• Early Release of Pan Am Lockerbie Bomber Stirs Controversy