6 Unit-Conversion Disasters

Think you had a bad day at work? At least you didn't lose spacecraft worth hundreds of millions of dollars. Forgetting to convert measurement units can result in big-time disasters—like these six examples.

1. A satellite lost communication with Earth.

In 1998, NASA lost equipment worth millions thanks to shoddy conversion practices. SOHO, the Solar Heliospheric Observatory, a joint project between NASA and the European Space Agency, lost all communications with Earth. After about a week of technicians trying various solutions, communication was restored and everyone breathed a sigh of relief.

Among the problems thought to have caused the sudden blackout? An error in the spacecraft’s navigation measurements of nearly 100 km, which resulted in a much lower altitude than expected.

2. NASA lost a Mars orbiter.

Can you imagine losing $125 million thanks to a little metric system error? That’s exactly what happened in 1999 when NASA lost a Mars orbiter because one team used metric units for a calculation and the other team didn’t. Guess they didn’t learn from their previous mistake.

3. A plane ran out of fuel mid-flight.

In 1983, an Air Canada plane ran out of fuel in the middle of a flight. The cause? Not one but two mistakes in figuring how much fuel was needed. It was Air Canada’s first plane to use metric measurements, and clearly not everyone had the hang of it yet. Luckily, no one was killed and only two people received minor injuries. That’s amazing considering the flight crew thought they had double the fuel they actually had.

4. A hospital patient overdosed on a sedative.

In 1999, the Institute for Safe Medication Practices reported an instance where a patient had received 0.5 grams of phenobarbital (a sedative) instead of 0.5 grains. A grain is a unit of measure equal to about 0.065 grams. The Institute emphasized that only the metric system should be used for prescribing drugs.

5. An aircraft flew with way too much cargo.

In 1994, the FAA received an anonymous tip that an American International Airways (now Kalitta Air, a cargo airline) flight had landed 15 tons heavier than it should have. The FAA investigated and discovered that the problem was in a kilogram-to-pounds conversion (or lack thereof).

6. Columbus miscalculated his New World destination.

The navigator miscalculated the circumference of Earth when he used Roman miles instead of nautical miles, which is part of the reason he unexpectedly ended up in the Bahamas on October 12, 1492, and assumed he had hit Asia.

A version of this story ran in 2010; it has been updated for 2021.