Going on a trip can be stressful enough without adding your dog to the mix. Some organizations, including the Humane Society of the United States recommend against flying with your dog at all because of numerous cases where the animals didn't arrive safely. But if you'll be taking to the skies with Fido in tow, some advance planning can ensure that both you and your pet will be ready for takeoff.

Assess whether your dog can handle the trip.Radio show host and pet travel expert Stephanie Abrams points out that every breed and every dog has its own temperament that can affect your trip. "Some by nature are more high-strung," she says, and not good at dealing with the motion and the other rigors of travel. If your dog is relaxed in the car, that is a good sign. Certain breed-specific physical characteristics can make travel difficult, for instance brachycephalic dogs such as pugs and shih tzus have a pushed-in muzzle that often causes breathing problems which makes traveling in airplanes -- and especially the cargo hold -- risky.
Veterinarian David Smith of the New York Department of Agriculture agrees: "Be realistic about whether or not your pet is a good candidate for air travel. If your pet is easily stressed out by new environments, it may be better to leave it with a trusted pet-sitter." (The U. S. Department of Agriculture and state agriculture organizations are involved with the rules regarding transport of live animals.)

Know the airline rules.
These can vary quite a bit. Many airlines, like American Airlines, require that animals be at least 8 weeks old at the time of travel. Most airlines say that an animal under 20 pounds (including the weight of the pet carrier) can be brought aboard as long as the carrier can fit underneath the seat. Some allow larger animals to be flown in the cargo hold, but not all. For instance Jetblue has an extensive JetPaws Pet Program but passengers can only bring a pet as carry-on.
Not all customers feel comfortable having their pets travel kenneled in the airplane's cargo hold. It can be extremely stressful for both the dog and the owner -- especially with recent news reports of dogs being lost or sent to the wrong destination. If your dog is small enough to fit in its carrier underneath your seat, you'll probably want to travel that way. Fees vary per carrier and can be anywhere from $75-200. A good resource for comparing airlines is PetTravel.com, which has the lowdown for every major carrier. Once you've narrowed your choices, go directly to the airline site to get the most updated rules. If you plan to have your dog in the cabin, it's important to make a reservation for your dog at the same time you are booking your flight, because every airline has a limited number of animals they will allow on board.
The Air Transport Association recommends that, "whenever possible, book a direct, nonstop flight and avoid holiday or weekend travel. Consider schedules that minimize temperature extremes. For example, try to avoid travel during excessively hot or cold periods. Morning or evening flights are preferable during the summer."

Get the essential paperwork done.
Many airlines require a certificate of health that has been completed by the vet within two weeks of traveling certifying that they've given your dog a clean bill of health. Also consider making sure your dog can be identified if anything happens. Dr. Smith says, "I would recommend some form of permanent, non-removable identification, either a tattoo or a microchip."
Check into any particular health requirements or necessary quarantines at your destination. To take your pet abroad can require months of testing and preparation, notes Dr. Smith. But even Hawaii has strict regulations about bringing in pets.

Prepare your dog for travel.
Rachel Farris, spokesperson for PetRelocation.com, tells customers, "The most important thing you can do to prepare your pet emotionally as well as physically for the trip is to get him used to his pet travel crate well in advance. Acclimate the pet to his travel crate ahead of time by leaving the crate in a common area of the home or feeding your pet his meals in the crate on a daily basis." When your dog is happy with his carrier, he will be more relaxed and also less likely to overheat because he will be breathing normally, lowering his body temperature.
While you might be tempted to give your pet a little something to take the edge off the stress of travel, don't. Abrams says that you should not sedate your dog because it can cause breathing problems, make their stomach upset and can also affect their equilibrium. She also suggests not feeding your dog the night before a morning flight so that your dog won't be as desperate to go do its business. Having said that, some airports have dog parks and "pee stations" that you may want to be aware of if your travels get delayed. Check to see if the airports you'll be using have those facilities and find out where they are located.