#3 Air traffic control systems use Linux to get you from A to B safely

U.S. has ported its FAA's (Federal Aviation Administration) Common ARTS software to Linux.  Common ARTS (or Automated Radar Terminal System) is an air traffic control computer system that air traffic controllers use to track aircraft.The computer system is used to automate the air traffic controllers job by correlating the various radar and human inputs in a meaningful way. This system is being used in most of the TRACONs around the United States. Common ARTS is the most modern implementation of ARTS in use at various locations in the United States.

#2 Nuclear submarines need Linux to run

The United States Department of Defense uses Linux - "the U.S. Army is “the” single largest install base for Red Hat Linux" and the US Navy nuclear submarine fleet runs on Linux. In 2004, Lockheed Martin delivered a nuclear submarine to the US government that was powered by Red Hat Linux.

#1 Google, Amazon, and Facebook all use Linux for various web and cloud services

Some of the biggest players in internet arena like the search giant Google, the largest social networking site Facebook and biggest online merchant Amazon, all use Linux for various services.

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