My wife and I have flown with eight different dogs of our own over the last 30 years. We find that a dog does in a plane exactly what it does in a car. If that includes barfing, be ready (or don't try it). If that includes barking continuously, be ready for that, too (including some comments from ATC if they hear a dog in the background). If that including racing around the vehicle like a maniac, put the dog in a travel container. If that includes hanging his head out the window and barking, either keep the window/canopy shut or be ready for stares and pointing while you taxi.
We've seen no indication that the noise bothers them, but I suppose that if you flew a lot with them, they could sustain the same type of hearing problems that pilots do without ear protection. I've heard of some folks putting cotton in their dog's ears -- personally, I'd hate to try it on ours (remember the last time you had to give your dog medicine?), and anyway, I think they'd dig it out as fast as they could. I've also seen the "Mutt Muffs" on the internet, but the dog wearing them in the picture looked ready to rip the arm off the person who put those things on his head.
Tranquilizers have never seemed necessary for our beasts, but I'd say that if their behavior in the car is such that you couldn't stand it in the plane, you'd best trank them. But experiment with this - you'd be amazed how those things affect a dog, and how long it takes to a) take effect, and b) wear off. When we shipped two dogs on TWA from England to the U.S., the airline required them to be crated and tranquilized. The vet gave us pills, and suggested half a pill for each dog (and these were both retrievers – not small dogs) a couple of hours before flight. We gave the dogs the pills, and there was no immediate effect. About an hour later, the dogs, well, melted. They just slowly sank into a heap and z'd out. We got to the airport and tried to give them one last walk to drain the sumps before flight. They walked up to this fire plug outside the terminal that had obviously been used by many other dogs for the same purpose, and sniffed it intently. Then they tried to make their final salute to the British Empire – and were unable to get a leg up without collapsing. The poor beasts just stood there, looking sadly at the fire hydrant, and then at us, as if to say, "I really want to, but I just can't do it." It then took two of us to stuff the virtually limp dogs into their crates.
As far as crates/restraints, again – judge by car experience. If the dog moves around too much to stand in a plane, you’d best either crate or restrain them. There are a number of restraints available for automotive use, and they should work fine in the plane, although our Black Lab would immediately set to chewing through such restraints – she was either loose or crated to the day she died. The other point is that an unsecured dog can become a missile hazard. We were cruising along in IMC over BDR with our Chocolate Lab Chewbacca. He was curled up in the back, sound asleep (as he normally did in cruise flight). We hit a downdraft and dropped about 50 feet. I looked back as we dropped, and saw a) daylight between the dog and the floor, b) two big yellow eyes the size of dinner plates, and c) four legs splayed out trying to find something on which to hold. Shortly after the airplane stopped descending, the dog caught up with a thump. Chewie spent the rest of the flight wide awake, trying desperately to dig in and hang on to the floor.
Cats are a whole ‘nother story. The worst one I heard was a guy ferrying his wife’s cat from NY to Florida in a Bonanza. Somewhere over North Carolina the uncontained cat got spooked and went crazy, tearing all over the cabin, clawing/scratching/biting him. By the time he got on the ground (after declaring an emergency), there was blood everywhere – all his. No way any live cat gets in my plane other than in one of those cat boxes.
As for the pressure changes, yes, I have noticed one effect. Some years back, we had Chewie in the back of the Cheetah as we climbed up to about 11,000 feet or so from sea level (summer day, looking for smooth air). We forgot how much methane gas is trapped in the digestive tract of a Labrador, and that the gas expands in volume as outside air pressure decreases, while the dog's gut is limited in size. Passing about 5000 he began to whimper and look uncomfortable. Passing about 8000 feet the smell hit us (gas only -- no solid waste). We turned around and he settling down, looking very satisfied. Fortunately, a Cheetah has a canopy that can be opened in flight, providing the necessary ventilation for us to survive.
Duke, a Golden Retriever, was my principal pooch passenger for several years in the Cougar. He thoroughly enjoyed going ANYwhere, and was a delight in the plane. When we arrive at the airport, he hopped up on the wing, and went right into the back seat where he sat up watching the world out the window until takeoff, and then sprawled across the back seats, snoozing until he felt the wheels go down. Then it was back up to that beautiful Golden Retriever sitting position for landing, watching out the window until we stopped, then out the door and down to see what there was new at this airport that he hadn’t seen before. But when we went back to the airplane, it was hippity-up onto the wing, and he was ready to fly again.
Of late, we have begun flying rescued Aussies for the Aussie Rescue Placement and Helpline (ARPH), making us the charter members of ARPHAir, of which Bill Greenburg was the second pilot, and others have now joined the effort. In that situation, not knowing the dogs, we mount a crate in the back of the plane (Grumman 4-seaters have flop-down rear seats) and that's where they go. After an hour or so in cruise, if the dog is relaxed, we may open the gate for a bit of reassuring petting, but if any doubts arise, the dog stays locked up. We had one who oozed his way into the front seat, and then wanted to sit in my lap while I was flying -- not cool. He got stuffed back in the crate and left there for the rest of the flight, during which he stared long and hard at the latch, trying to figure out how to open it. As far as sedation, I know that the effects of sedatives are increased with altitude, and without knowing for sure the effect on any given dog or the altitude at which we'll fly, we do not sedate them. We give specific instructions to that effect to the sending ARPH volunteer, and will not accept the dog if sedated (don't want a bad reaction at 7000 feet). We put the dog in the crate before engine start, and then see what happens when we crank. If the dog really freaked, that would be the end of the flight right there, but so far, there hasn't been a significant reaction.
