TSA and powder rules
In the United States, TSA allows powders in carry-on but containers larger than 12 ounces or 350 grams may require additional screening at the checkpoint and in some cases must be moved to checked baggage. Most matcha tins are well under that threshold. Keep the original sealed tin where possible so the contents are easy to identify.
Packing for the trip
Slip the tin into a zip top bag inside a hard sided pouch so it cannot be crushed in transit. Keep it out of direct sunlight in your bag and avoid leaving it in a hot car or window seat. International rules vary, so check the security agency for your departure and arrival countries before flying.
Hotel room brewing without a chasen
A small fine mesh strainer doubles as a sieve. A travel sized milk frother or a clean shaker bottle can stand in for the chasen. Pre dissolve 2 grams of matcha in 30 to 40 milliliters of warm water in a cup, shake or froth until smooth, then top with hot or cold water. The texture will be lighter than a chasen bowl but the flavor holds.
On the go shaker method
Add 2 grams of sifted matcha and a small splash of cool water to a sealed shaker bottle. Shake hard for 10 seconds to fully hydrate the powder, then add cold water or milk to your preferred strength and shake again briefly. This is the most reliable way to avoid clumps when you are working with kettleless tap water on a train or in an airport.