How many power banks can I take on board?
Up to 2 per person (160Wh or less only; from April 24, 2026). They cannot be put in checked baggage.
Source: Japan Ministry of Land, Infrastructure, Transport and Tourism (MLIT): new rules for carrying power banks on board (announced April 14, 2026; applied from April 24, 2026) [in Japanese] (retrieved 2026-09-27)
Can I charge my phone on board?
Do not charge from a power bank. MLIT asks passengers to charge electronic devices using the onboard power outlets.
Source: MLIT: "To All Passengers: Regarding Bringing Power Banks on Board" (English version) (retrieved 2026-09-27)
Can I take a 20,000mAh power bank on board?
At a rated voltage of 3.7V, it is 74Wh, which is in the 100Wh-or-less category. In practice, calculate with the rated voltage or Wh shown on the product.
Source: MLIT: "To All Passengers: Regarding Bringing Power Banks on Board" (English version) (retrieved 2026-09-27)
Can I put spare batteries in my suitcase?
Neither power banks nor removed spare batteries can go in checked baggage. Carry them on board.
Source: MLIT: "Examples of Dangerous Goods by Air Transportation" (English version, last updated April 24, 2026) (retrieved 2026-09-27)
Does the 100ml rule apply to domestic flights too?
According to MLIT, the 100ml / clear bag rule applies to international flights. The quantity limits for toiletries, medicines and sprays (0.5L per container, 2L per person) also apply to domestic flights.
Source: MLIT Civil Aviation Bureau: "Security Control for Screening Liquids, Aerosols and Gels (LAGs) carried into International Passenger Flights departing from Airports in Japan" (English version) (retrieved 2026-09-27)
Source: MLIT: "Examples of Dangerous Goods by Air Transportation" (English version, last updated April 24, 2026) (retrieved 2026-09-27)
Can I carry eye drops or liquid medicine on board an international flight?
In the amount needed in the cabin, they are an exception to the 100ml limit. Declare them at security screening. In containers of 100ml or less, you can also carry them in the clear bag without declaring them.
Source: MLIT: "List and Description of LAGs Restriction" (English version of the list of liquids, 2015) (retrieved 2026-09-27)
Can I use a Japanese hair dryer in South Korea?
It depends on the "INPUT" label on the product. South Korea uses 220V (per the IEC list), so if it says 100-240V, you can use it (plug types C, F). If it says only 100V, do not use it as is.
Source: IEC (International Electrotechnical Commission) World Plugs country list (as of June 2025). The IEC no longer publishes this list, so a copy is kept on this site (retrieved 2026-09-27)
Do I need a plug adapter in the United States?
In the IEC list, the United States uses types A and B, the same as Japan (A, B). The voltage is 120V, so also check the product's "INPUT" label.
Source: IEC (International Electrotechnical Commission) World Plugs country list (as of June 2025). The IEC no longer publishes this list, so a copy is kept on this site (retrieved 2026-09-27)
Can I take a cordless hair iron?
If the heating part and the battery can be separated, it is allowed in carry-on and checked baggage with conditions. If not, it is not allowed in either.
Source: MLIT: "Attention! Customers purchasing hair care items: Check that your purchase can be taken on board your aircraft!" (English version) (retrieved 2026-09-27)
How much alcohol can I bring home?
Under the flight rules: 24% or less has no quantity limit as dangerous goods, over 24% up to 70% is limited to 5L per person, and over 70% is not allowed. Customs duty-free allowances are separate rules.
Source: MLIT: "Examples of Dangerous Goods by Air Transportation" (English version, last updated April 24, 2026) (retrieved 2026-09-27)
For every answer, some airlines may have stricter rules. In the end, follow your airline's guidance.