Please note that Alaska Airlines has changed its policy re health certificate for in-cabin pets three times since early December 2014. Here’s my most recent post about this maddening situation. Since I’ve learned that Things Change, often Without Warning, I urge you to click on the link I’ve provided for each airline name to double-check the current policy.

The first thing to know is that individual states make their own rules about the movement of pets across their borders. The USDA’s APHIS (Animal and Plant Health Inspection Service) website makes that clear: “USDA APHIS VS, our agency, does not set requirements for the movement of pets across state lines. The requirements are actually set by each individual state. Therefore, you should contact the State Veterinarian of the state you are traveling to. They will provide you with the requirements.”

Oh, great, you’re saying — I have to figure out the rules for each state I’m flying to with my dog. And what if my flight is diverted to a state I hadn’t researched? Officially, you’re right. Here are the things you need to ponder (please note that Hawaii is horribly complicated and will get a separate post):

• Nearly all of the states require that dogs over 12 weeks old be vaccinated against rabies, so it’s simplest to have your dog vaccinated at 12 weeks, put the rabies tag on her collar, and hang on to her most current vaccination certificate. A handful of states allow you to wait until she’s 4, 5 or even 6 months old, so if you’re anxious about vaccinating, you’ll want to look at each state’s rules.
• Nearly all of the states require a Certificate of Veterinary Inspection (typically called a “health certificate”), signed by a veterinarian and saying that your dog is fit to travel and up to date on all of her vaccinations. Some don’t, including California.
• If you’re driving between states, or through several states, you may want to consider how likely it is that the issue will ever come up. Will I get a health certificate for Chloe when we drive to Eastern Oregon to visit my uncle later this year? Probably not, even though Oregon would like me to.
• Flying is a different story. All U.S. airlines require you to obtain a health certificate before flying to another state with your checked dog, and you’ll be asked for that document by the ticketing agent. Most U.S. airlines don’t require that an in-cabin pet have a health certificate. (As you’ll see in the chart below, the only exceptions are Alaska Airlines and Hawaiian Airlines — and again, you should expect that the ticketing agent will ask for documentation.) Since it costs about $30 to get a health certificate, if you’re flying on a carrier other than Alaska or Hawaiian, you may decide it’s worth it to do some quick research and see whether your plans are taking you between states that don’t have a health certificate requirement. (You may, in fact, decide that even if the states on your itinerary do have a health certificate requirement, you’ll take the risk. I’d be lying if I said I hadn’t, myself.)
• One final twist is that a health certificate is only good for 30 days after your vet signs it. Keep in mind that both ends of your journey need to be covered by the certificate, and don’t strand yourself in another state with a just-expired certificate. As you’ll see in the chart below, some airlines require that the certificate be issued within 10 days of travel, and others require that it be issued within 30 days of travel. If you’re going to get a health certificate for your dog, it’s simplest to get one within 10 days of travel.

What happens, you ask, if your certificate does expire while you’re still on vacation? One airline, Allegiant, has thought about the problem, and offers a solution. [2/4/12 Allegiant no longer requires health certificates, so the airline’s neat solution (“If a certificate is accepted on the originating flight, it will be accepted on the return flight if it is within 180 days of the originating flight and if the return flight was booked with the same itinerary as the originating flight. If a current veterinary certificate is not available, a current shot record on appropriate veterinary letterhead will be accepted.”) no longer appears on Allegiant’s website]. Otherwise, you’ll need to locate a vet and schedule an appointment, have your dog’s records faxed over, and get a new certificate issued for your return trip.

If you want to dig into specific state and airline requirements, you’ll need USDA APHIS’s handy link to each state’s import regulations. And here’s a chart showing which major U.S. airlines require a health certificate for your dog (and which don’t), and when a certificate needs to be issued. Table last updated April 15, 2013. This is the kind of information that rapidly goes out of date, so be sure to check the current rules for the airline you’re planning to use, using the links I’ve provided in the first column.