Can you take hair mousse on a plane?

On a domestic flight only the quantity limits apply. On an international flight the liquid rule comes on top.

Domestic flights in Japan

The 100ml liquid limit does not apply.

International flights from Japan

Each container 100ml or less, all of them inside one transparent re-sealable bag of 1 litre or less, one bag per person.

Mousse comes out as foam, yet every list judges the can it comes out of.

Korea files mousse with hairspray, not with gel or wax

Korea's aviation security site has an entry for 헤어무스 (hair mousse), and its wording matches the entry for hairspray and cooling spray: 500ml (0.5kg) or less per container, up to 2L (2kg) per person. The entries for hair gel and hair wax on the same results page carry no such figures and just say cabin and checked baggage are both possible.

Shaving foam is the stand-in on the other lists

No European or Hong Kong source in hand names hair mousse. They name its nearest relative. The European Commission ends its definition of liquids with perfumes and shaving foam, GOV.UK lists sprays including shaving foam, and Hong Kong airport's FAQ answers yes to whether shaving foam qualifies as LAGs: containers of not more than 100ml, inside the 1-litre plastic bag.

The only mousse on Japan's liquids list is a dessert

The Japanese edition of the liquids list prints ムース once, in the desserts row between jelly and mitsumame. Hair mousse is not written anywhere. The row that fits the can is the toiletry aerosol block, where hair spray and shaving foam appear, and the main list of restricted items gives shaving foam a line of its own in the cosmetics class.

A capped valve is written into the allowance

Hong Kong's CAD makes the cap a condition of carrying a toiletry aerosol at all: release valves must be protected by a cap or other suitable means to prevent inadvertent release of the contents. The UK CAA's table repeats that condition and adds that the release of gas must not cause extreme annoyance or discomfort to crew members.

The TSA lists other foams and aerosols, not mousse

The TSA's item list has no mousse entry. Its closest one is Shaving Cream (aerosol), allowed in carry-on at 3.4oz/100 ml or less. The agency's liquids rule is wide enough to take in a can of mousse without naming it: it covers liquids, aerosols, gels, creams and pastes, in travel-sized containers of 3.4 ounces (100 milliliters) or less per item.

The carry-on answer for hair mousse is the same in all 7 other places we checked. The limits themselves are not identical, so read the row for the country you fly from.

Each row comes from that authority's own page. Airlines can be stricter, and the screening officer has the final say.

What to do

Move hair mousse to the bag you check in before you reach security, within the checked-baggage limits above. Narita Airport states that anything given up at the checkpoint is discarded and cannot be returned.