Liquids, gels, and aerosols must be in containers that are 3.4 ounces (100 ml) or smaller. Note that larger, half-full containers are not allowed. and: TSA Permitted and Prohibited Items List.

As of 2026, whether you can bring a 300ml container of liquid in your carry-on depends entirely on the technology available at your specific airport. Many major international hubs, including London Heathrow, Gatwick, and several airports in the EU and Asia, have fully implemented advanced 3D CT (Computed Tomography) scanners. These airports have officially scrapped the old 100ml rule, allowing passengers to carry liquids in containers up to 2 litres without removing them from their bags. However, if you are traveling through an airport that has not yet upgraded its security equipment, you are still strictly limited to containers of 100ml or less, which must all fit inside a single one-litre transparent bag. Always check your departure and return airports' current rules; if even one airport on your journey still uses older technology, your 300ml bottle will be confiscated at the security checkpoint unless it is an exempt item like baby milk or essential medication.