Flying with pets has the potential to be stressful for all involved. Fortunately, in my experience few people and animals suffer significant problems in the process.
First, check with your airline to determine what their regulations and requirements are. As well, familiarize yourself with the laws regarding transport of animals into the state or territory of your destination. Your pet may need certain vaccines or a health certificate prior to travel. Your veterinarian should be able to help you work through the legal and bureaucratic technicalities involved in flying with your pet.
When you fly, keep your pet with you if possible. Often, cats and small dogs can be brought on board as carry-on “luggage.” Keep your pet in a small but comfortable and well-ventilated carrier. Place a towel or fleece on the bottom of the carrier and keep another towel handy in case your pet soils the first one. On long trips, you can offer your pet water occasionally, but I don’t recommend placing a water bowl in the carrier if your pet will be traveling with you. Pets can suffer motion sickness, but it is rare and usually not severe.
It is possible to tranquilize pets prior to travel, but tranquilizers usually aren’t necessary for pets who are calm when in their carriers. If you have doubts, try placing your cat in the carrier and driving around for a while to see how he reacts. If you want tranquilizers, your vet should be able to provide them.
Believe it or not, X-ray machines at airports use very low doses of radiation, and in theory you could send your pet through the machine and it won’t hurt him. However, the security screener may be willing to perform a hand search of the carrier, which would make X-ray screening unnecessary. Some people have sent the empty carrier through the machine and walked through the metal detector carrying their pet. This should be done carefully–you don’t want your pet jumping from your arms and escaping into a crowded airport.
It is unlikely that your cat will catch a cold while flying. People catch colds on flights because we are cooped up with hundreds of other people in tight quarters. Germs spread well in such conditions. Fortunately, cats aren’t susceptible to most human pathogens, so your cat probably won’t be exposed to any dangerous viruses on the flight. However, the stress of traveling may weaken his immune system and make him more susceptible to other types of infection.
It is very likely that pets’ ears pop on flights, but they can’t complain about it and therefore nobody knows for sure. Although pets can’t chew gum, you could leave a chew toy in the carrier. It might help to relieve the pain of pressure equalization in his ears.