This from the Nikon Pro magazine:
by Julian Hollingshead

“New restrictions on carrying batteries on aeroplanes – how does this affect me if I’m carrying Nikon batteries?

The International Civil Aviation Organisation recently issued a change to its Dangerous Goods Regulations, affecting how Lithium-ion (Li-ion) batteries can be carried on flights. They apply to these batteries depending on output, measured in Watt hours (Wh).

Under the new regulations, batteries under 100Wh are exempt from carrying restrictions. Nikon batteries are all below 28Wh in output.

The new regulations state that an electronic device containing a Li-ion battery (such as a camera) can be carried along with a maximum of two spare Li-ion batteries. These should not be put into checked baggage but should be carried as hand luggage.

If you are unsure about any of these restrictions, we would recommend that you speak to the airline you are travelling with to check the policy details regarding carrying Li-ion batteries before you fly.

When transporting spare batteries we recommend that they be individually packaged and the battery terminals insulated by fitting the plastic battery terminal cover supplied with all Nikon batteries.”