UFO means Unidentified Flying Object. The firefighter manual says what to do if an unidentified aircraft or object crashes. To read all mentions of "UFO" as "alien spacecraft" shows the limits of knowledge of the reporter and/or commenters, not the manual's writers.

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"If this were play'd upon a stage now, I could condemn it as an improbable fiction."
Shakespeare, Twelfth Night
Illuminati's Razor-The most complicatedly evil answer is usually the most correct answer. - Fazor
"Every book is a children's book if the kid can read." - Mitch Hedberg
"Distance doesn’t matter much in space, where if you just start a thing off with the right kind of shove, sooner or later it will get where you want it to go." -Frederik Pohl, Mining the Oort