Investigation Summary
The investigation revealed that the bomb was contained in a package mailed from Munich, intended for an Israeli El Al flight but rerouted to Swissair due to scheduling changes. The device utilized an altimeter-based trigger, designed to detonate once the aircraft reached a specific altitude. The resulting explosion in the aft cargo hold caused localized temperatures high enough to melt aluminum alloys, weakening the airframe's structural integrity while the plane was still in flight. As the fire spread, smoke filled the cockpit, forcing the crew to use oxygen masks and eventually obscuring their view of the flight instruments. The loss of electrical power in the final minutes rendered the aircraft uncontrollable, leading to a high-speed impact in the Unterwald forest.
Final Conclusions
The crash was caused by the detonation of an improvised explosive device in the aft cargo compartment. The explosion led to a catastrophic in-flight fire, loss of cabin pressure, and the eventual failure of critical electrical systems. The inability of the crew to see their instruments due to dense smoke was a significant factor in the loss of control. The investigation identified members of the PFLP-GC as the primary suspects, though the criminal case was officially closed in 2000 without any convictions.
Video Analysis
Caught In The Crossfire | The Deadly Bombing Of SwissAir 330 — A detailed look at the 1970 bombing of Swissair 330, including ATC recordings of the crew's final moments and the technical investigation into the in-flight fire.
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Airframe & Maintenance
Systems & Failure Modes
Aft Cargo Compartment
Location of the bomb detonation and subsequent intense fire.
Electrical System
Failed approximately 12 minutes after the explosion, leading to a total loss of control.
Flight Instruments
Rendered useless to the crew due to dense smoke filling the cockpit.
Interesting Facts
- 01The bomb was triggered by a barometric sensor (altimeter) set to detonate at a specific altitude.
- 02A second bomb exploded on an Austrian Airlines flight the same day, though that aircraft landed safely.
- 03The flight was carrying 15 Israeli citizens and a significant amount of mail.
- 04The Convair 990 Coronado was the fastest subsonic passenger jet of its era.
- 05Investigators found that the cargo hold metal had been exposed to melting temperatures for 11 to 13 minutes before impact.
Safety Actions & Advisories
Montreal Convention 1971
The bombing led directly to the adoption of the Convention for the Suppression of Unlawful Acts against the Safety of Civil Aviation.
Postal Security Changes
International mailing practices were altered, with several countries temporarily banning airmail to Israel in favor of surface mail to prevent similar attacks.
Known Controversies & Unanswered Questions
Alleged Secret Deal with the PLO
Reference ↗Journalist Marcel Gyr alleged that Swiss authorities made a secret deal with the PLO to grant diplomatic immunity in exchange for no further attacks on Swiss targets. A 2016 parliamentary inquiry found no evidence to support these claims.