Airline Rules About Stainless Steel Tumblers Or Mugs They say that you can bring a mug in your carry-on if the travel mug or tumbler is empty, doesn't resemble a weapon, and has no sharp edges or features. So yes, you can bring a travel mug on a plane.

You can absolutely bring an insulated coffee mug on a plane in 2026, but it is a high-fidelity requirement that the container is completely empty when you pass through the security checkpoint. The TSA and international security agencies like CATSA classify coffee mugs, thermoses, and "Stanley-style" tumblers as liquid containers; if they contain even a small amount of coffee or water, they will be confiscated or you will be asked to dump them. Once you are past security, you can fill the mug at a water station or have a coffee shop fill it for you before boarding. If you are carrying a modern electric self-heating mug, you must ensure the battery is under 100Wh and follow standard "High-Fidelity" electronics rules. Packing it in your checked luggage is also perfectly safe, though wrapping it in clothing is a high-fidelity best practice to prevent the vacuum seal from being damaged by rough handling during transit.