The size restrictions of airlines are determined by the type of aircraft being used and the amount of overhead space versus passenger count. While some airlines allow one carry-on with a total weight of 40 pounds or less and a total size of 45 inches or less (length + width + height), others permit passengers to bring only 18 pounds at a total size of 22 x 16 x 8 inches. The range is substantial and should be investigated prior to arrival at the airport. In addition to one carry-on piece of the permissible dimensions, a computer case, handbag or shopping bag is also allowed.
Restrictions on sharp items, explosives, weapons, liquids in containers with more than 3.4 ounces and items deemed dangerous by airport security cover all commercial air travel around the globe. This may include items you do not immediately recognize as dangerous such as nail clippers or food items.
If traveling premium first class on some international airlines, special allowances for checked and carry-on limits are made. Long-haul international flights also tend to be more lenient with carry-on amounts than shorter, international flights. Airlines considered by most to be premium service carriers are typically more lenient regarding carry-on items than discount airlines
