Flashlights are required on commercial flights I believe. They are usually on a wall mount in the galley area. I just don't think people are at all likely to have a problem. There is a thread in the technology (or possibly travel products - it predates the splitting of those forums) on travel lights. I don't recall anyone mentioning problems and lots of people were carrying lights. I have had Surefires be noticed by TSA and security in other countries but never an issue past identifying it as a flashlight.