Each individual airline must file with the FAA their rules about carry-on bags. The FAA is responsible to the airlines to make sure they adhere to these rules. The FAA can and do impose fines if the airline is not compliant with their own rules.
Most Airlines have similar rules about carry-on bags on domestic flights.
International Carriers have other rules. You must check with each airline for the most up-to-date information.
What can I carry-on?
1 Carry-on bag that can fit in the overhead bin
1 Small Personal item under the seat in front of you.
Carry-on bag cannot exceed 40 lbs or 45 Linear inches W x H x L.
Small personal items would be a purse, briefcase, small backpack.
Musical Instruments may be carried on. It is considered your carry-on bag. No other bag is allowed. You may also have a personal item.
If there is no room for the instrument, it can be gate tagged, that means it will be brought up to you on the Jetway at the end of the flight.
There are other accommodations for large instruments. You may be required to purchase a seat. Check with the airline you are traveling with.
Cabin pets are considered your carry-on-bag. No other bag is allowed. You may also have a personal item. The pet carrier must be 19 inches x 13 inches x 9 inches. Must fit under the seat. There are soft side carriers too.
Sometimes the airlines run out of room on a flight. If you are at the end of boarding, you may be required to gate check your carry-on-bag.
Make sure you remove fragile items, valuable items, passports, medicine, car keys. No electronic cigarettes or spare lithium batteries are allowed in checked bags.
Other items not included in your carry-on allotment would be:
Wheelchairs
Car-seats
Baby strollers
CPAP
Crutches
Canes
Pillow/Blankets
Diaper bag
Small amount of food
Remember, carry-on space is limited and shared space with fellow travelers.
Do not put Coats, personal items in the overhead.
You must be able to pick up your bag and put it in the overhead, Flight Attendants are NOT allowed to help you with this. Make sure it can fit and it is not to heavy.
Enjoy the Journey!