Carry-on baggage is a small piece of luggage you keep with you in the overhead cabin of the aircraft while flying. Some airlines allow you this one carry-on bag for free in addition to one personal item. (Personal items are usually kept on the floor under the seat in front of you and include items such as a laptop computer, purse, small backpack, briefcase or camera case). However, some airlines may charge a fee for the overhead carry-on bags. Please check with your specific airline for their official policy regarding the cost and size restrictions for carry-on luggage.
The Transportation Security Administration (TSA) will screen every carry-on bag and personal item that will fit through the x-ray machine. Please note that although a carry-on bag may fit inside an x-ray machine, it may not meet size regulations and be oversized for a particular airline. It is up to each individual airline as to whether you will be able to carry on a particular bag. It is best to contact your carrier before traveling to confirm their carry-on policy. Or check with your airline at the terminal before proceeding through the security checkpoints.
For information on screening procedures for gate-checked and larger items that will not fit through x-ray machines (strollers, car seats, wheelchairs, etc.), please visit this section of the TSA website.
Always keep your belongings in sight during screening. You are responsible for your property as it proceeds through the screening process.
Checked baggage is luggage you check in at an airline's ticket counter or curbside if available. These bags will not be accessible during your flight. TSA is mandated by federal law to screen 100% of checked baggage. Bags may need to be opened during this process. When locking your checked bags, please use a TSA Accepted and Recognized Lock. If your baggage needs to be opened and inspected, TSA may have to break unrecognized locks to access your bags. TSA will not reimburse passengers for unrecognized locks broken as a result of the security screening process.
For additional tips, go here.