For guidance, the Transportation Security Administration refers travelers to its “Can I bring it?” Web page, which features a search tool that addresses what items are and are not permissible on airplanes. Here’s a sampling of TSA advice. Keep in mind that even if an item is identified as generally permitted, the TSA cautions “it may be subject to additional screening or not allowed through the checkpoint if it triggers an alarm during the screening process, appears to have been tampered with, or poses other security concerns. The final decision rests with TSA on whether to allow any items on the plane.”