6–8 Weeks Before

Call your airline directly to confirm pet policyRules on carrier size, in-cabin vs. cargo, breed bans (especially snub-nosed/brachycephalic breeds), and how many pets are allowed per flight vary a lot and change without much notice.
Book your pet's spot when you book your own ticketAirlines cap the number of animals per flight; waiting means you may not get a seat for your pet at all.
Check destination country or state import rulesInternational travel, Hawaii, and some territories have their own quarantine or paperwork requirements that take weeks to satisfy.
Ask your vet if your pet is fit to flyAge, brachycephalic breeds, heart conditions, and severe anxiety can all be reasons a vet advises against air travel.
Buy an airline-approved carrier now, not the week of the trip if flying or crate requiredGive your pet time to get comfortable in it before the trip.
Book pet-friendly lodging and confirm rules if road trips overnight stopsIncluding any weight or breed limits.

3–4 Weeks Before

Schedule the vet visit for your official health certificateMost airlines and many states/countries require the exam and paperwork within 10 days of travel; timing matters, book the appointment now so it lands in that window.
Update vaccinations, especially rabiesMany destinations require rabies shots at least 30 days old but not expired; get this sorted before it becomes a last-minute scramble.
Ask your vet about microchipping if your pet doesn't have oneStrongly recommended everywhere, since it's the main way you'd be reunited if your pet gets loose in transit.
Discuss sedation with your vet — and expect them to say noSedating pets for air travel is generally discouraged because it can affect breathing and balance at altitude; don't medicate on your own.
Order a nutrition/water dispensing bowl that clips to the carrier if cargo hold only

Get the health certificate signed within the required windowOne-shot deadline. If your travel date slips, you may need a new exam.
Double-check carrier dimensions against airline specsCargo carriers need enough room for your pet to stand, turn around, and lie down; too small and it'll be rejected at check-in.
Label the carrier with your contact info, destination address, and "Live Animal" stickers if cargo checked petsThis is often required and is your pet's ID if the carrier gets separated from you.
Trim nailsSo they don't catch in carrier grates.
Practice several short trips in the car and the carrierTo reduce in-transit anxiety.
Freeze a water dish if cargo checked petsSo it melts gradually instead of spilling in transit.

Confirm the flight and pet reservation againSchedule changes happen and cargo holds have temperature restrictions that can bump pets off a flight with little warning.
Check the forecast for departure and connection cities if cargo hold petsAirlines typically embargo pet cargo travel above roughly 85°F or below about 45°F at any airport on the route; a hot or cold snap can ground your pet even if your own flight goes ahead.
Pack a travel kit: food, collapsible bowl, waste bags, a favorite blanket or toy, any medications, and copies of all paperwork
Print and pack extra copies of the health certificate and vaccine recordsDon't rely on a phone screen if a form gets lost or an airline/border agent wants a paper copy.
Feed a light meal a few hours before departure, not right beforeTo reduce the odds of motion sickness.

Arrive early — pet check-in takes longer than regular check-inAirlines typically require extra time to process paperwork and load animals into cargo.
Attach an ID tag with your cell number to your pet's collarA second layer of ID in case of separation.
Walk your pet right before security/boardingSo they're empty and calmer going in.
Remove the leash/collar before placing your pet in a checked/cargo carrier if where requiredA dangling leash or tag can catch on crate doors; keep the leash accessible for pickup.
Take a current photo of your pet on your phone right before drop-offUseful for a lost-pet report if anything goes wrong in transit.
Ask ground staff to confirm your pet is loaded and get a name/confirmation if cargo holdSo you have a point of contact if there's a delay.

Pick up your pet from the correct cargo/oversize baggage location promptlySome airports charge fees or involve animal control if pets aren't collected within a set window.
Check your pet over for signs of stress, dehydration, or injury before leaving the airport
Offer water in small amounts first, then a normal meal once they've settled
Update your address on the microchip registry if relocation not round trip
Keep your pet indoors or leashed for the first day or two in a new environmentDisorientation increases the risk of bolting.