What (not) To Pack > Prohibited Items
In the aftermath of the World Trade Center and Pentagon attacks, the list of items that may not be brought into aircraft cabins has grown considerably longer, and the actions of security personnel more zealous. Although the Transportation Security Administration (part of the U.S. Department of Transport) publishes an official list of both prohibited and permitted items, its existence doesn't necessary predict what will happen at the airport, where the personal views of random security personnel may have a greater impact on your travel experience. This is even more the case in developing countries, where the rules sometimes seem to be made up on the spot. There's little you can do about any of this, other than be polite: a pleasant smile, a calm attitude, and a little deference (whether justified or not) will always serve you better than grumpiness and belligerence.
There are also constraints on the carrying of liquids, gels, and pastes into aircraft cabins. U.S. rules pertaining to this can be found at the TSA link above; European regulations are similar. Travelling with liquids, which are heavy, bulky, and leakage-prone, is best avoided (or at least limited) in any event.
