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Join Date: Sep 2006
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I looked at TSA's "Can I bring?" on this.
Flash light (two words) is allowed in carry-on, subject to screener discretion.
Flashlight (one word) is apparently classed as a 'tool' and is subject to the 7-inch rule.
Flashlights (one word, plural) is allowed in carry-on, subject to screener discretion.
OP should be fine. Subject to screener discretion, of course.