SHORT ANSWER
Organizing international pet shipping from the US is complicated because no single agency or company owns the whole process. Your destination country writes its own entry rules and can change them at any time. A USDA-accredited veterinarian has to prepare the health certificate, and USDA APHIS has to endorse it. Federal animal welfare rules limit the temperatures pets can be exposed to at US airports, the IATA sets crate size standards, and each airline decides whether it will accept your pet on a given route and date. Every one of these requirements runs on its own clock, and they all have to line up for the same departure day.
The first thing that surprises most families is that the US government does not tell you what your pet needs to leave. It tells you where to look. On its export page for pet travel, USDA APHIS explains that "your destination country sets the entry requirements for pets, which can change at any time," and that owners must verify the requirements every time they plan to travel.
That means a family moving to Japan, a family moving to Portugal, and a family moving to Australia are working from three completely different checklists. One country may only need a microchip, a rabies vaccination, and a health certificate. Another may require a rabies antibody blood test, an import permit, and a waiting period. Australia, for example, will not accept a dog from the US until at least 180 days after the rabies titer blood sample reaches an approved laboratory, according to the Department of Agriculture, Fisheries and Forestry.
Because these rules are set abroad and updated on each country's own schedule, advice from a friend who moved two years ago, or even a checklist you saved last spring, may already be out of date.
Leaving the US with a pet requires paperwork from two different parties, and both have to get it right.
First, you need a USDA-accredited veterinarian. APHIS says this vet will help you determine your destination's requirements, confirm your pet meets them, and submit the health certificate to APHIS for endorsement on your behalf. Not every vet does this work. Accreditation is a separate federal credential, and many general practice clinics do not issue international health certificates at all.
Second, APHIS itself has to endorse the certificate, typically through its electronic Veterinary Export Health Certification System (VEHCS). APHIS lists the details your vet will need to get this right, including the destination country, any countries where your pet will stop on the way, your departure date, and whether your pet is flying as cargo or in the cabin with a person.
Each of those details changes which form applies. A single mismatch, such as a microchip number transposed on one line or a vaccination date entered incorrectly, can send the certificate back for revision. When a flight is only days away, that correction loop is where many do-it-yourself moves run into trouble.
Most people think of pet shipping as a list of tasks. It is more accurate to think of it as a set of countdown clocks that all have to reach zero on the same day.
Some requirements have to happen months ahead, like a rabies vaccination or a titer test with a mandatory waiting period. Others have to happen within days of the flight, like the final vet exam and health certificate, which many countries require within a short window before arrival. APHIS endorsement has to fit inside that same short window. And the airline has its own booking and acceptance rules layered on top.
Under federal rules, carriers cannot accept a dog or cat for transport more than four hours before the scheduled departure, and the shipper has to certify in writing that the pet was offered food and water within the four hours before drop-off, according to 9 CFR 3.14. Even the day-of timing is regulated.
If any one clock slips, the others do not wait. A flight change can push you past the validity of a health certificate. A late lab result can push you past your lease end date. This is why experienced coordinators build the timeline backward from the arrival date instead of forward from the first vet visit.
Weather is one of the least understood complications, because it has nothing to do with paperwork.
The Animal Welfare Act regulations set minimum standards for how dogs and cats are handled in transit. Under 9 CFR 3.19, the temperature in an airline's animal holding area must not fall below 45°F or rise above 85°F for more than four consecutive hours while dogs or cats are present. Under 9 CFR 3.14, pets also cannot be exposed to temperatures below 45°F for more than 45 minutes while being moved to or from the aircraft, and a carrier can accept a pet for colder conditions only with a veterinarian's acclimation certificate dated within 10 days of drop-off.
Each airline also sets its own seasonal and temperature policies on top of these federal minimums, and those policies vary by carrier, route, and airport. The practical result is that a heat wave at your departure airport, or a cold snap at a connection point, can delay a pet even when every document is in order.
The travel kennel is not a shopping decision you can leave to the last week. The International Air Transport Association publishes container requirements that airlines use to judge whether a crate is acceptable. According to IATA's Traveler's Pet Corner, a pet must have enough room to stand, sit erect, turn around normally, and lie in a natural position.
IATA provides a formula based on your pet's measurements. Minimum internal length equals nose-to-tail-base length plus half the height from ground to elbow. Minimum width is twice the width across the shoulders. Minimum height is the pet's standing height to the top of the head or ear tip, plus bedding. IATA also notes that snub-nosed breeds need a container about 10% larger and does not recommend transporting snub-nosed dogs such as boxers, pugs, bulldogs, and Pekingese during hot seasons.
A larger crate can also narrow your flight options, because not every aircraft can load every kennel size. Our guide to IATA-compliant crates walks through how to measure your pet and what hardware the kennel needs.
Your destination is not always the only country that matters. APHIS asks accredited vets to account for any countries where your pet will stop for customs clearance or where the pet leaves the airport or seaport on the way. IATA's guidance likewise asks owners whether they plan to break the journey at an intermediate station.
A connection that looks convenient on a booking site can add a transit requirement, a longer layover in a facility that may not be staffed for animals, or a route that an airline will not book for pets at all. Routing is a regulatory decision as much as a scheduling one.
Families on temporary assignments, military orders, or multi-year contracts often forget that the move has a second half. According to the CDC's dog importation guidance, the requirements for returning to the US with your dog depend on where your dog was vaccinated and what countries it has been in during the six months before entry. A dog that has been in a country CDC considers high-risk for dog rabies, and is not vaccinated, will not be allowed to enter.
Keeping your US vaccination records current and knowing your destination's risk classification before you leave can make the return trip far simpler.
The paperwork correction loop is not hypothetical. In an r/TravelWithPets thread titled Vet had to resubmit form to USDA to correct error, a pet owner moving from the US to the EU described being days from departure: "One of our two cats got their papers back and is good to go but our vet made an error on our other cat's form." Two pets, the same vet, the same flight, and only one set of paperwork was ready. That is exactly how a small clerical mistake turns into a race against a departure date.
None of these steps is impossible on its own. The difficulty is that they are owned by different organizations that do not coordinate with each other, and a pet owner is usually managing all of it in the middle of their own move.
"When families ask me why this is so hard, I tell them it's because nobody is in charge of the whole thing," says Adam Melton, VP of Strategic Initiatives at Starwood Pet Travel. "The destination country, the USDA, the airline, and the weather all get a vote, and none of them check with each other first. Our job is to be the one party looking at every clock at the same time, so a problem gets caught in week two instead of at the check-in counter."
For a deeper look at the risks involved and how destination rules, export paperwork, and airline policy interact, read our Rules & Risks of Pet Travel complete guide. When you are ready to plan your pet's move, you can request a free quote or contact our team.