This comes almost 32 years after the failed attempt at Karachi airport.
The attack, which occurred aboard Pan Am Flight 73 during an airport stopover in Karachi on Sept 5, 1986, resulted in the death of 20 passengers and crew.
The victims included citizens of the United States, India, Pakistan, Britain, Italy, Denmark, Ireland, and Mexico. There were 365 passengers and 16 crew members onboard on that flight.
"No matter how much time has passed or the obstacles we encounter, we owe it to the victims and their families to never give up on them," the Dawn quoted the FBI case agent, as saying in a statement released to the media along with pictures of the four hijackers.
In a bid to make the four hijackers identifiable, the FBI has age-progressed photos of them, Wadoud Muhammad Hafiz al-Turki, Jamal Saeed Abdul Rahim, Muhammad Abdullah Khalil Hussain ar-Rahayyal and Muhammad Ahmed al-Munawar.
The U.S. State Department has also offered a USD 5 million reward for information leading to their arrest.
The FBI has legally bound to continue the search as two Americans were also among those killed in the attack. (ANI)