Most domestic airlines allow passengers to bring one carry-on bag and one personal item on board. Personal items include diaper bags, purses, camera bags, laptop cases and backpacks. The items must comply with standard size requirements for carry-ons unless they're considered special items by the airline. Typically, airlines ask that passengers bring personal items that are small enough to fit under the seat in front of them to save room for larger bags in the overhead compartments.
You can take certain necessities on the plane without them counting as a carry-on or personal item. Some are exempt from typical size requirements set by the airline, such as strollers, child safety seats, wheelchairs and crutches. Other items the airline might consider special include pillows, blankets, umbrellas, outerwear and food. Most domestic airlines allow passengers to bring these items on board at no extra cost.
Every airline has its own policies regarding the maximum dimensions of carry-on luggage. Typically, for U.S. airlines, carry-on bags must not exceed 45 inches in combined length, width and height. Check your airline's specific size requirements online before selecting your bag, because your airline will have you check your carry-on if it's too large.
Policies regarding the contents of carry-on luggage are set by the Transportation Security Administration rather than by airlines. The TSA has a lengthy list of items prohibited from being packed in carry-on luggage, including weapons, items that can be used as weapons, explosive chemicals and more. A full list of prohibited items can be found on the TSA's website. Additionally, the TSA limits the amount of liquids passengers can bring in their carry-ons. In most cases, only 3.4 ounces of each liquid is allowed. Breast milk, formula and medication are exempt from the 3.4-ounce rule and can be packed in reasonable quantities in carry-ons.
