What size dog can I take on a plane?

All the rules you need to know before you book a trip for your dog in the cabin or the cargo hold of a plane

The recent death of French bulldog Kokito has many pet parents and animal lovers concerned. The owner of the dog, Catalina Robledo, was traveling with her 11-year-old daughter Sophia Ceballos, 2-month-old son and Kokito on a March 12 United flight from Houston to New York City.

The family was seated, with Kokito in a carrier under the seat in front of Robledo, when a flight attendant insisted that the dog's carrier, which the attendant said was blocking the aisle, be placed in the overhead bin.

"And we're like, 'It's a dog, it's a dog.' And she's like, 'It doesn't matter you still have to put it up there,' " Ceballos told Good Morning America. "She helped her put it up, and she just closed it like it was a bag."

United spokesperson Maggie Schmerin told PEOPLE "our flight attendant did not hear or understand her, and did not knowingly place the dog in the overhead bin."

Kokito ended up traveling in the overhead bin for the duration of the three-hour flight, barking from the bin at least 30 minutes into the trip. When Robeldo went to get her dog at the end of the trip, she discovered the canine had died.

"A stranger offered to hold her newborn while she sat on the floor, there in the airplane aisle. She was holding her dog and rocking back and forth. Her daughter was also crying," fellow passenger Maggie Gremminger told PEOPLE about the heartbreaking moment.

This tragic death and the following criminal investigation have led to a larger discussion about dog owners' rights when traveling with their pets, and what the rules are when it comes to air travel and canines.

Your dog's weight, temperament, carrier and more can change what rules you have to follow during plane travel. Before you get on a plane with your dog, make sure you know what to expect and what restrictions the airlines have.

To make it easier for traveling dog owners everywhere, PEOPLE has rounded up everything you need to before boarding a plane with your pooch.

Traveling with Small Pet Dogs 

Most domesticated dogs weighing 20 pounds or less are allowed to travel with their owners in the cabin of the plane. Owners cannot simply bring their pets on board. There are several rules and restrictions that dog owners must follow before they travel to get the okay to bring their small canines on with them.

Registration: Most flights only allow a limited number of pets on board, and most major airlines (aside from JetBlue, which has online registration) require that you call the airline in advance to let it know a small dog will be traveling with you. It's best to inform the airline as early as possible because if all the pet spots for your flight are filled when you call, they will not allow your dog to fly with you on that flight. If the dog you are traveling with is a service or emotional support animal, this limit does not apply.

Fees: As part of your registration process, you will have to pay a fee to bring your pet on board. These fees are usually between $95-$150 each way and apply to pets, but not to emotional support animals and service animals.

Carriers: If your dog is flying in the cabin, it has to travel in a TSA-approved pet carrier (soft-sided or hard-sided) that is well ventilated and can fully fit under the plane seat in front of you. Each airline has its own size restrictions on pet carriers, make sure to check ahead of time that the carrier you are planning to use fits.

Pre-Flight Paperwork: Many airlines do not require dog owners to provide health records for their pet prior to the flight, though pet policies are changing. Delta now requires anyone traveling with an animal to provide health and vaccination records at least 48 hours before the flight. Pet owners traveling with Delta also have to sign a behavior voucher, stating that their animal will behave for the duration of the flight. Regardless of whether the airline you are using requires paperwork or not, it is always smart to travel with your dog's medical records and license in case there is an issue during your trip. Make sure to check before your trip what paperwork your airline requires and if the destination (especially tropical destinations) you are traveling to requires records, as well.

Age Restrictions: Some airlines do not allow young dogs to travel in-cabin with their owners. Check with your airline to see if there are age restrictions if you are traveling with a dog 16 weeks old or younger.

Baggage: Your pet carrier will count as a carry-on bag or personal item, so make sure to pack accordingly. If you want to bring a carry-on and a personal item on to the flight in addition to your pet's carrier, you will have to pay for an extra bag. At some airlines, up to two pets are allowed to travel in one carrier, as long as the carrier and the animals don't weigh more than 20 pounds together.

International Travel: Most airlines will not allow you to travel with a small pet dog in the cabin on an international flight or on a flight where you are connecting to an international flight. In these cases, your small dog will have to travel in the cargo hold. There are some exceptions. Check with your airline to see what international travel it allows with an in-cabin pet.

Check in: If you are traveling with a pet in-cabin, you must check-in at the airport with your pet. It is important to leave time in your travel schedule to check your pet in at the counter since you will not be able to check them in online or at a kiosk.

Security: Pets do not go through the x-ray machine for baggage. When you reach security, remove your pet from its carrier and send the carrier through the x-ray machine. You and your pet will walk through security together and then you can place them back in the carrier.

At the airport: Dogs must stay in their carriers while at the airport unless they are using a pet relief area. If the airport does not have pet relief areas, you and your dog will have to leave the airport and return through security.

On-board: On the plane, your small pet dog must remain in the carrier at all times. You cannot remove the animal from the carrier while on the plane. The carrier containing your dog can only go completely under the seat in front of you. Carriers cannot be stored on your lap, in an overhead bin or anywhere else. Your dog must remain in its carrier under the seat in front of you for the duration of the trip.

Behavior Rules: Airlines have the right to have you and your pet removed from a flight, or to deny you and your pet boarding if your dog acts aggressively towards airline staff or other travelers.

Purple Collar Pet Photography/Getty

Traveling with Larger Pet Dogs

Dogs over 20 pounds, unless they are emotional support or service dogs, will have to travel in the cargo hold of the plane. Not all airlines offer this option, since the cargo hold needs to be pressurized to allow pet travel. When you are planning a trip with a larger dog, make sure the airline you are using offers a travel option for larger pets. Cargo hold travel differs from in-cabin travel in many ways, but the biggest is that you will not have access to your pet during your flight. Your dog will spend the entirety of the flight, including tarmac delays, in the cargo hold, where there can be fluctuations in temperature.

Booking a Cargo Hold Trip: Most airlines don't allow you to book a pet via cargo until 10 days before your trip. Check to see when your airline allows pets traveling in cargo to be booked and try to set your pet's travel plans as early as you can to prevent stress down the line.

Crate Requirement: Larger dogs should be in a crate that is large enough for them to move and stand freely, including turning their head. It also needs to be large enough for them to stand and sit without the top of their head or ears touching the roof of the crate. Crates also need to have a solid roof with no holes and one secure-close metal door. Crates need to be made of rigid material that does not bend when pressure is applied. For cargo travel, you will likely need to buy a different carrier than the one you have, since most pet carriers have materials and design elements not permitted for cargo travel.

Documentation: The documents required for your pet's travel varies based on where you are traveling from and where you are going. Contact both the consulate of the countries you are traveling to and your veterinarian to make sure your dog has all the required paperwork for your trip. The airline will require all travelers sending their pets through cargo to fill out forms for the airline and to provide a health certificate from the dog's vet. This health certificate must be issued shortly before your pet travels (usually 10 days or less). If you are going on a long trip with your dog, you may be required to get a new health certificate for the return trip.

Age Restrictions: There are age restrictions for pets traveling via cargo. If your dog is 16 weeks or younger, contact the airline you are traveling with to ensure that your pet can fly in the cargo hold.

Breed Restrictions: Every airline that flies pets through cargo has different breed restrictions. Some breeds of dogs (like English bulldogs) may be prohibited from flying due to breathing problems they may encounter during the trip. Other breeds are allowed to fly, but only during certain months, in certain carriers and at certain ages. These restrictions are for your pet's safety. Make sure to check with your airline that your dog is allowed to fly in its cargo hold.

Rates: Rates vary based on your destination and the size of your pet. Travel fees for pets traveling via cargo usually start around $200 one-way.

Pick-up and Drop-off: To have your dog flown through cargo you will need to drop them off at a special location at least 2 to 3 hours before your flight and then pick them up at the cargo location of your destination, which is usually different from where you pick up your bags. Check with the airline you are using to see when they require pets to be dropped off at cargo and where the cargo pick-up and drop-off locations are for your trip. Leave extra time in your travel schedule to make these stops as stress-free as possible.

Traveling with Emotional Support Animals

If you have an emotional support dog, you can travel with your animal, often free of charge, as long as you prepare the correct paperwork and your dog can fit comfortably on your lap or in the space in front of your seat. Exact size restrictions vary for each airline as do paperwork requirements. Most airlines need a letter from your doctor that is less than a year old (and meets several requirements), stating that your dog is flying with you to help with a mental or emotional condition. Your emotional support animal can be denied boarding or removed from the plane if it shows aggressive behavior to passengers and/or flight staff. Contact the airline you are traveling with to understand the specific paperwork it requires and to inform them that you are traveling with an emotional support animal.

America’s VetDogs and Guide Dog Foundation/Rebecca Eden

Traveling with a Service Dog

Service dogs travel free of charge. Delta now requires that service dog owners submit health records at least 48 hours before their flight. To prevent issues at the gate, check with the airline you are flying with to see if any paperwork is required prior to boarding. Service dogs are allowed to sit on their owner's lap or in the space in front of their seat.