Airline Rules About Stainless Steel Tumblers Or Mugs Take the TSA, for example. 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.

Yes, insulated tumblers (such as those from Stanley, Yeti, or Hydro Flask) are allowed through airport security in 2026, provided they are completely empty when you go through the X-ray scanner. Security agencies like the TSA are concerned with the contents of the container, not the material of the bottle itself. Once you have cleared the security checkpoint, you are free to refill your tumbler at an airport "Hydration Station" or coffee shop and take the full container onto the plane. This is a high-value strategy for travelers because it allows you to stay hydrated with your preferred water temperature throughout a long flight without relying on small plastic cups from the cabin service. A peer-to-peer tip: ensure the lid is tightened properly before putting it back in your bag, as the pressure changes in the cabin can sometimes cause minor leaks. Size is generally not a constraint for an empty bottle, though an exceptionally oversized "gallon-sized" jug might take up significant space in your carry-on luggage.