According to the F.A.A. website, carry-on luggage cannot exceed 45 linear inches in size. This is measured by adding the length, width and height of the luggage. Oversized or irregularly shaped luggage within this limit must fit into the overhead storage bins during the flight or it will be checked. Weight of your carry-on is limited by individual airline regulations, which can be range from 11 pounds to as much as 40 pounds.
Liquids must be in bottles no larger than 3.4 oz. in volume. These bottles must be packed into a 1 quart-sized, clear, plastic, zip-top bag. Passengers are limited to one bag each, which must be scanned separately from other carry-on luggage. Liquids such as medications, baby formula or food can exceed the 3.4 ounce limitation, but must be declared during the screening process.
The Transportation Safety Administration has updated the rules regarding many previously restricted carry-on items. For example, passengers are allowed to carry one personal cigarette lighter in their carry-on luggage, but are not allowed to carry extra fuel. You are also allowed to carry one pack of standard safety matches, but not "strike anywhere" matches. On a somewhat humorous note, the TSA does allow passengers to carry a personal parachute, but you are not allowed to wear it during the flight.
Carry-on rules concerning items required by disabled or special needs passengers should be reviewed prior to your flight. Items such as wheelchairs, portable oxygen, needles, canes and or special medicines are generally allowed, but must meet certain restrictions. Additionally, these items are subject to excess baggage charges if they exceed the airline allowances.
Passengers who intend to carry questionable items or items exceeding TSA regulations, in their carry-on luggage should arrive at airport security early, to allow extra screening time. Items that cannot be screened using an x-ray machine or standard screening methods may be required to undergo special screening which may require additional time to complete.
