A Libyan intelligence official accused of making the bomb that brought down Pan Am Flight 103 over Lockerbie, Scotland, in 1988 in an international act of terrorism is to appear Monday in federal court in Washington to face charges.

The arrest and extradition of Abu Agila Mohammad Mas’ud Kheir Al-Marimi are a milestone in the decades-old investigation into the attack that killed 259 people in the air and 11 on the ground.

The Justice Department announced Sunday that Mas’ud had been taken into U.S. custody, two years after it revealed that it had charged him in connection with the explosion. Two other Libyan intelligence officials have been charged in the U.S. for their alleged involvement in the attack, but Mas’ud would be the first defendant to appear in an American courtroom for prosecution.

His appearance was set for 1 p.m. EST. The New York-bound Pan Am flight exploded over Lockerbie less than an hour after takeoff from London on Dec. 21, 1988. Citizens from 21 countries were killed. Among the 190 Americans on board were 35 Syracuse University students flying home for Christmas after a semester abroad.

The bombing laid bare the threat of international terrorism more than a decade before the Sept. 11, 2001, attacks. It produced global investigations and punishing sanctions while spurring demands for accountability from victims of those killed. Several victims described as surreal the news that Mas’ud was finally in American custody.