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Space agencies were some of the first places where you could find open source software “in the wild”. Being natural early adopters, cash-strapped and very inquisitive, the agencies naturally took to the open source concept. Additionally they were some of the first users of ARPAnet and subsequently the Internet, which which lit a fire under the open source movement. Today this marriage between rocket science and open source saw its latest victory with the landing of NASA’s Phoenix Mars Lander.

via OStatic

Apparently, the aerospace industry makes heavy use of free, *nix-based custom software for almost every mission. The U.S. military has already using/developing free software, and companies in the aviation business are most likely looking to use free software for their applications.