10 Famous Software Disasters

We all know software bugs can be annoying, but faulty software can also be expensive, embarrassing, destructive and deadly.  Following are 10 famous software “disasters” in chronological order:

​1.  Mariner Bugs Out (1962)

​Cost: $18.5 million

​Disaster: The Mariner 1 rocket with a space probe headed for Venus diverted from its intended flight path shortly after launch.  Mission Control destroyed the rocket 293 seconds after liftoff.

​Cause: A programmer incorrectly transcribed a handwritten formula into computer code, missing a single superscript bar.  Without the smoothing function indicated by the bar, the software treated normal variations of velocity as if they were serious, causing faulty corrections that sent the rocket off course.

2.  Hartford Coliseum Collapse (1978)

​Cost: $70 million, plus another $20 million damage to the local economy

​Disaster: Just hours after thousands of fans had left the Hartford Coliseum, the steel-latticed roof collapsed under the weight of wet snow.

​Cause: The programmer of the CAD software used to design the coliseum incorrectly assumed the steel roof supports would only face pure compression.  But when one of the supports unexpectedly buckled from the snow, it set off a chain reaction that brought down the other roof sections like dominoes.



3.  CIA Gives the Soviets Gas (1982)

Cost: Millions of dollars, significant damage to Soviet economy

Disaster: Control software went haywire and produced intense pressure in the Trans-Siberian gas pipeline, resulting in the largest man-made non-nuclear explosion in Earth’s history.

​Cause: CIA operatives allegedly planted a bug in a Canadian computer system purchased by the Soviets to control their gas pipelines.  The purchase was part of a strategic Soviet plan to steal or covertly obtain sensitive U.S. technology.  When the CIA discovered the purchase, they sabotaged the software so that it would pass Soviet inspection but fail in operation.



4.  World War III… Almost (1983)

Cost: Nearly all of humanity

​Disaster: The Soviet early warning system falsely indicated the United States had launched five ballistic missiles.  Fortunately the Soviet duty officer had a “funny feeling in my gut” and reasoned if the U.S. was really attacking they would launch more than five missiles, so he reported the apparent attack as a false alarm.

​Cause: A bug in the Soviet software failed to filter out false missile detections caused by sunlight reflecting off cloud-tops.



5.  Medical Machine Kills (1985)

​Cost: Three people dead, three people critically injured

​Disaster: Canada’s Therac-25 radiation therapy machine malfunctioned and delivered lethal radiation doses to patients.

​Cause: Because of a subtle bug called a race condition, a technician could accidentally configure Therac-25 so the electron beam would fire in high-power mode without the proper patient shielding.



6.  Wall Street Crash (1987)

​Cost: $500 billion in one day

​Disaster: On “Black Monday” (October 19, 1987), the Dow Jones Industrial Average plummeted 508 points, losing 22.6% of its total value. The S&P 500 dropped 20.4%.  This was the greatest loss Wall Street ever suffered in a single day.

​Cause: A long bull market was halted by a rash of SEC investigations of insider trading and by other market forces.  As investors fled stocks in a mass exodus, computer trading programs generated a flood of sell orders, overwhelming the market, crashing systems and leaving investors effectively blind.



7.  AT&T Lines Go Dead (1990)

​Cost: 75 million phone calls missed, 200 thousand airline reservations lost

​Disaster: A single switch at one of AT&T’s 114 switching centers suffered a minor mechanical problem and shut down the center.  When the center came back up, it sent a message to other switching centers, which in turn caused them to shut down and brought down the entire AT&T network for 9 hours.

​Cause: A single line of buggy code in a complex software upgrade implemented to speed up calling caused a ripple effect that shut down the network.





8.  Patriot Fails Soldiers (1991)

Cost: 28 soldiers dead, 100 injured

​Disaster: During the first Gulf War, an American Patriot Missile system in Saudi Arabia failed to intercept an incoming Iraqi Scud missile. The missile destroyed an American Army barracks.

​Cause: A software rounding error incorrectly calculated the time, causing the Patriot system to ignore the incoming Scud missile.

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9.  Pentium Fails Long Division (1993)

​Cost: $475 million, corporate credibility

​Disaster: Intel’s highly-promoted Pentium chip occasionally made mistakes when dividing floating-point numbers within a specific range. For example, dividing 4195835.0/3145727.0 yielded 1.33374 instead of 1.33382, an error of 0.006%.  Although the bug affected few users, it become a public relations nightmare.  With an estimated 5 million defective chips in circulation, Intel offered to replace Pentium chips only for consumers who could prove they needed high accuracy.  Eventually Intel replaced the chips for anyone who complained.

​Cause: The divider in the Pentium floating point unit had a flawed division table, missing about five of a thousand entries and resulting in these rounding errors.





10.  Ariane Rocket Goes Boom (1996)

​Cost: $500 million

​Disaster: Ariane 5, Europe’s newest unmanned rocket, was intentionally destroyed seconds after launch on its maiden flight.  Also destroyed was its cargo of four scientific satellites to study how the Earth’s magnetic field interacts with solar winds.

​Cause: Shutdown occurred when the guidance computer tried to convert the sideways rocket velocity from 64-bits to a 16-bit format.  The number was too big, and an overflow error resulted.  When the guidance system shut down, control passed to an identical redundant unit, which also failed because it was running the same algorithm