For many of us, pets are a part of the family. They eat the same food, sleep in our beds and some even dress better than other humans. So when it comes to flying, travelers want the best for their pets. Here’s what you need to know:

The basics

It might sound like a no-brainer, but the first question you should ask yourself is, “Is your animal a pet?” According to the FAA, a pet refers to dogs, cats, ferrets, rabbits, rodents, hedgehogs, reptiles, amphibians, and birds. It’s important to note that birds like turkeys, chickens, doves and geese do not count as pets.

When it comes to service animals, the rules are totally different. These animals are not considered pets, and are seen as workers with a job to do. Service animals are typically dogs and airlines don’t charge a fee for them to fly. Many travelers with physical impairments travel with these animals that provide support, guidance, and assistance to their owner. Travelers flying with a service animal are typically asked to provide a credible verbal assurance stating the animal’s purpose and supporting documentation from a doctor. Those traveling with emotional support animals also need a doctor’s note. These animals come in many forms (pigs, turkeys, even monkeys) and owners avoid paying fees because the animal is said to help them deal with the anxiety of flying. The practice, however, has gotten so out of control that the Department of Transportation is currently debating if airlines should adopt a stricter policy on what kinds of service animals should be allowed on planes.

Many airlines require health certificates for your pet or service animal to travel. According to VetInfo, the certificate involves a veterinary consultation and the cost of vaccines, so it can cost anywhere from $35 to $200 if you’re pet’s shots aren’t up to date.

Safety first

If you have a small animal weighing less than 20 pounds, most airlines will charge you $125 to $150 to carry-on your pet. Every airline requires that your animal be placed in a carrier that can comfortably fit under the airplane seat.

For animals over 20 pounds, nearly every airline requires you transport your pet in a kennel in the cargo area of the plane. This can cost anywhere from $150 to $600 depending on the airline, size of the dog and destination. This practice has become controversial because of the risks. From May 2005 to July 2016, the Department of Transportation reported that 320 pets died while flying in the cargo area of planes. This figure includes 247 dogs, 48 cats and 6 birds. During this period, 82 of the animal deaths occurred on Delta, 64 died on United Airlines and 51 on American Airlines.

In response, airlines like Delta have strengthened their pet programs over the past year by providing safer transportation options and closer monitoring. Still, if you’re worried about your pet’s safety, it might be worth your time to consider other options. Many people choose to kennel their dog or hire a dog walker to stop by the house a few times a day while out of town. Each of the options can cost anywhere from $25 to $50 a day depending on where you live.

Every airline has slightly different domestic pet policies; here’s a breakdown from five major US carriers.

American Airlines (AAL)

Carry on: To carry on a pet, the animal must be at least 8 weeks old, and it must have a kennel that comfortably fits underneath the seat. The airline will charge a fee of $125 for flights within and between the US, Canada, Mexico, the Caribbean, Central America and South America.

Checked: To check a pet, owners must contact the airline at least 48 hours prior to arrival, however, pets are accepted on a first-come basis, so it’s crucial to plan ahead. Checking a cat or dog will cost approximately $200 per kennel.

More from American Airlines.

Delta (DAL)

Carry-on: To carry on your pet, your animal must be small enough to fit comfortably in a kennel without touching or protruding from the sides. The kennel or carrier must be able to fit under the seat directly in front of you. Your pet will count as one piece of carry-on luggage.

In the US and Canada, travelers will pay $125 USD to carry on their pet.

Checked: Delta stopped checking pets with baggage in March, and today, travelers choosing to transport their animals underneath the plane can use a program called Delta Cargo. This option guarantees that your pet will get transported to the plane in temperature-controlled vans and will be monitored closely by customer service teams. The price varies greatly depending on the size of your animal and the distance flown, but a one-way trip can cost between $300 and $600.

More from Delta.

JetBlue (JBLU)

Carry-on: JetBlue has a program called JetPaws to help customers decide the best way to travel with their animal. Program membership is free and includes a carrier bag tag and members earn 300 TrueBlue points on each segment when flying with a pet. However, travelers still have to pay a $100 pet fee each way. Your animal can travel in the cabin as long as its carrier does not exceed 20 pounds or 17 inches long x 12.5 inches wide x 8.5 inches high.

Checked: Animals are not permitted as checked baggage on JetBlue.

More from JetBlue.

Southwest (LUV)

Carry on: To fly in the plane cabin, your pet must be able to fit in a carrier with the maximum dimensions of 18.5 inches long x 13.5 inches wide x 8.5 inches high. The carrier will be considered one of your carry-on items and must remain under the seat in front of you for the entire flight. Southwest charges owners a $95 pet fare each way.

Checked: Animals are not permitted as checked baggage.

More from Southwest.

United Airlines (UAL)

Carry-on: Like the other airlines, United allows pets in the cabin if they are transported in a carrier that fits under the seat. The maximum dimensions for hard-sided kennels are 17.5 inches long x 12 inches wide x 7.5 inches high, and the maximum dimensions for soft-sided kennels are 18 inches long x 11 inches wide x 11 inches high. The airline will charge a $125 fee each way.

Checked: United’s PetSafe program promises to safely transport your pet in the aircraft cargo area while awarding you 500 MileagePlus miles for each shipment. Prices vary, but customers traveling in the US can expect to pay anywhere from $200 to $963 depending on the weight of the animal.

More from United.

Brittany is a writer at Yahoo Finance.

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