Baggage. Your pet carrier will count as a carry-on bag or personal item, so pack accordingly. If you want to bring a carry-on and a personal item onto the flight in addition to your pet's carrier, you will have to pay for an extra bag.
Can I have a carryon and a pet?
Yes. Pet carriers are considered either a personal item or a carryon item. You may board the aircraft with either a pet carrier and a personal item or a pet carrier and a regular size carryon bag.
How big of a dog can fit under an airplane seat?
Generally, if your dog in its carrier can fit under the seat in front of you, it can go in the cabin. So that means a dog weighing up to about 20 pounds.