Flights Gone Wrong

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What Changed After Pan Am 103: How Airport Security Evolved

Pan Am Flight 103 was destroyed by a bomb hidden in a suitcase over Lockerbie, Scotland, on 21 December 1988, killing 270 people. This guide explains what the investigators found about the aircraft’s break-up and how airport and airline security changed in the years that followed.

Published 6 min read

After Pan Am Flight 103, the rule that no checked bag should fly without its passenger, and the screening of checked bags for explosives, moved from good practice toward law. In the United States, a presidential commission found aviation security inadequate, and Congress passed the Aviation Security Improvement Act of 1990. The accident investigators also asked for research into making aircraft more resistant to explosions.

The bombing in brief

On 21 December 1988 Pan Am Flight 103, a Boeing 747-121 named Clipper Maid of the Seas, took off from London Heathrow for New York with 243 passengers and 16 crew. At 19:02:50, cruising at 31,000 feet over southern Scotland, it was destroyed by a bomb in its forward cargo hold.

All 259 people on board and 11 residents of Lockerbie were killed. A week later, forensic scientists found conclusive evidence of a detonating high explosive on recovered pieces of a baggage container, and the disaster became a criminal investigation. A Libyan intelligence officer was later convicted of the murders. The evidence is covered in Pan Am Flight 103: How a Tiny Fragment Traced the Lockerbie Bomb.

What the AAIB found about how the aircraft broke up

The UK Air Accidents Investigation Branch (AAIB) studied the technical side. It left the airport security and criminal aspects to a separate investigation (AAIB report 2/90).

Its findings, in plain terms:

  • The aircraft was airworthy and properly maintained. There was no defect that caused or contributed to the accident.
  • The bomb was in a luggage container loaded at position 14L in the forward hold. That put it about 25 inches from the skin on the lower left side of the fuselage.
  • The blast blew a large hole in the fuselage and disrupted the cabin floor. Cracks then ran outward from the hole, driven by the pressure difference between the cabin and the outside air.
  • Pressure waves from the explosion damaged structure well away from the bomb. Together, the direct and indirect effects destroyed the strength of the forward fuselage.
  • Containers and cargo thrown out of the hole struck the tail. The forward fuselage and flight deck separated within two to three seconds.
  • Most of the rest of the aircraft broke up as it fell almost vertically from 19,000 to 9,000 feet. The wing struck Lockerbie, causing a large crater and a fireball. See Pan Am Flight 103: How Investigators Proved a Bomb Over Lockerbie.

The AAIB’s cause: the in-flight disintegration was caused by the detonation of an improvised explosive device located in a baggage container positioned on the left side of the forward cargo hold.

The AAIB’s five recommendations

Four of the five recommendations were about flight recorders. The cockpit voice recorder had ended with a loud bang, and analysis of the recorders using the techniques of the time did not show positive evidence of an explosion. The AAIB asked for:

  1. Recorder buffers that keep their data when power is lost.
  2. Airworthiness authorities to reconsider letting buffered data sit in memory that is lost without power.
  3. A short back-up power supply, no more than a minute, so the cockpit voice recorder can capture events that cut the aircraft’s power almost instantly.
  4. A government-funded study of ways to record violent pressure pulses, ideally with the aircraft’s own recorders.

The fifth went to the aircraft itself. It asked airworthiness authorities and manufacturers to study measures that might lessen the effects of explosive devices and make aircraft structure and systems more tolerant of blast damage. Our guide to black boxes explains how recorder design has changed since.

Bag reconciliation: no bag flies without its passenger

The bomb on Pan Am 103 was in checked baggage. If a bag is loaded but its owner never boards, the bag may have been checked in by someone who does not intend to fly.

The US law that followed, the Aviation Security Improvement Act of 1990, required the FAA to address controls over checked baggage, naming as examples “measures to ensure baggage reconciliation and inspection of items in baggage of passengers” (Public Law 101-604). Reconciliation means matching every bag in the hold to a passenger who has actually boarded, and taking off any bag whose passenger has not.

Explosive detection and screening

The same Act set rules for explosive detection equipment. Before the FAA could require airports and airlines to buy and use it, the FAA Administrator had to certify, from tests designed with outside scientists, that the equipment could detect the amounts and types of explosive likely to be used to destroy an airliner, under real airline operating conditions. The tests had to be finished within 18 months. Until then, the FAA could order interim deployment if it judged that it would significantly improve security.

The Act also told the FAA to set up a programme to speed up research into technologies and procedures to counter terrorist attacks on civil aviation, starting with a review of which explosives posed the greatest threat to civil aircraft and the smallest amounts that could be expected to destroy one.

The commission and the 1990 Act

Congress based the Act on the report of the President’s Commission on Aviation Security and Terrorism, dated 15 May 1990. In the words of the Act’s findings, the commission “found that current aviation security systems are inadequate” to protect passengers of US airlines against terrorist threats.

The Act, signed on 16 November 1990, also:

  • created a post of Assistant Administrator for Civil Aviation Security at the FAA and a new Director of Intelligence and Security;
  • called on the US government to work through the International Civil Aviation Organization and directly with other governments to improve security at foreign airports and on foreign airlines;
  • required the State Department to assess its own response to the Pan Am 103 disaster;
  • gave a tax benefit relating to people killed in the Lockerbie bombing.

Cargo, containers and the aircraft itself

The AAIB’s fifth recommendation, to study how aircraft could better tolerate explosive damage, connects the investigation to later work on screening cargo as well as passenger bags, and on the containers bags travel in. We have not yet confirmed which of those measures were adopted and when, so this guide does not list them. It will be updated when we have the official sources.

Earlier and later bombings

Pan Am 103 was not the only airliner destroyed by a bomb in this period. Air India Flight 182 was bombed in 1985, and UTA Flight 772 in 1989. Neither has an event page on this site yet. When they do, they will be described as their official investigations found. The terrorism or sabotage topic page lists the events of this kind that are on the site now.

Remembrance

Two hundred and seventy people died: 243 passengers, 16 crew and 11 residents of Lockerbie. Behind the changes on this page are their families, the people of Lockerbie, and the investigators who spent years reconstructing what happened. The changes described here are part of what was done so that it would not happen again.

Where to go next

Watch in the library

Every video on this subject is on the Terrorism or sabotage page.

Sources

  1. AAIB (UK Air Accidents Investigation Branch). Aircraft Accident Report 2/90, Boeing 747-121, N739PA, Lockerbie, Dumfriesshire, Scotland, 21 December 1988 Read the report
  2. US Congress (GovInfo). Aviation Security Improvement Act of 1990, Public Law 101-604, 104 Stat. 3066 (16 November 1990) Source
  3. President’s Commission on Aviation Security and Terrorism (no verified URL). Report of the President’s Commission on Aviation Security and Terrorism, 15 May 1990 (cited in Public Law 101-604, section 2)

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