Well, my experience is fairly recent... let me share. First let me say, to fly in the cabin their is a size limitation. I'm not sure if it is different for the different airlines, but I imagine they are all similar. Delta's limit was 20 pounds including the carrier. The airlines also have a limit on the number of pets allowed in the cabin, so you have to call ahead and make all those arrangements (I'm sure you would anyway!). I was very nervous flying to get Guinevere and I asked every question you could imagine. The first flight I was scheduled on (for the return trip) was a puddle jumper. When I called Delta and questioned the size of the underseat storage they did change my flight to a larger plane with more room with no additional charge. The puppy had to be under the seat for the take off and landing. I bought a very nice carrier with lots of mesh openings and it was large enough for Guinevere to stand up and move around. Before I flew out of Phoenix I asked the attendant about my carrier; was the size okay? was I going to have trouble in Houston when I checked in? She told me she thought the carrier may be to large so she called a supervisor. The supervisor said it was fine. The attendant then told me to "stand my ground" in Houston and tell them the carrier was approved. Fast forward to the flight home!! I dropped off my rental car and made my way to the ticket desk. I was immediately told no to taking the puppy in the cabin in my carrier. They said it was too large. I told them it was approved in Phoenix and the top was flexible so it would easily fit under the seat. They said no. The ticketing agent said imagine the people around you watching you stuff a puppy under the seat. That makes us look bad. Luckily my flight was delayed. The pup and I headed out to the taxis I told the driver I needed to go to the petco. He barely spoke english and didn't know how to program his gps.. OMG, doesn't this guy get I'm running out of town and it's hot and I have a puppy in this carrier... fifteen minutes later we were finally on our way to the pet store. I guess he got that I was in a hurry (I remained nice, but rrrr), it was a crazy ride and I held onto the oh handle with one hand and the puppy/carrier with the other... I got to the store and ran back to the carriers and got a smaller one. I couldn't really put Guinevere down, she was only 11 weeks old and who knows about the other dogs that had been in the store. I took her out of one carrier, put her in the one I was going to buy and made sure she fit and had room to move. It wasn't ideal, but she did have room so we bought it and back to the airport. I walked up to the counter and they said it would be fine. I then sat down on the floor in the airport and took everything I had except the puppy and her stuff and shoved it in the original carrier and checked it and was then on my way thru security. The puppy was very warm and I was so worried about overheating. I went to one of the restaurants and got some food for me and then asked for ice. I took some ziplock bags and filled them and stuck them on the side pockets of the carrier to cool it off some. I wasn't allowed to take Guinevere out of the carrier and let her walk, so we made the best of it and boarded our first flight. We flew from Houston to Atlanta (because nonstop flights are almost impossibe these days!), it was a short flight. I safely tucked the carrier under the seat and we took off. I was told, by more than one person and on the website for Delta, that the carrier only had to be under the seat for take off and landing. I could then put the carrier on my lap but I was not supposed to even open the top. When the drink service came by the flight attendant literally yelled at me, everyone around me turned around and looked at me. She told me she was sure they told me when I checked in that the puppy had to stay under the seat and told me to put her back down there. I was almost in tears (which would not have been the first time that day!). That flight attendant was wrong, but how much of a fuss are you going to raise on a plane the way things are today... we made it to Atlanta and could not have been further from our connection. We were in the last gate on one side of the airport and had to run to the other side - also the last gate in that terminal. We missed our connection, by like 2 minutes! The plane was still there but they had done final boarding call. I just started crying, that poor ticket agent! They had already backed me up on another flight since I had a pet, but we had about an hour and a half in a very busy airport. There was no way I could go outside to let the puppy out for a potty and make it back in time, and was I really going to let her down in a designated pet area when she hadn't had all her shots. So I went into a bathroom stall and took her out and put her on my lap. I fed her and gave her a drink and cried. I spent a lot of time crying that day, and I am typically not moved to tears easily! The second, longer, flight was much better. We took off and I put the carrier on my lap. Everyone was excited to see a puppy even if it was thru a carrier (even the flight attendants). We made it home and the hubby picked us up at the airport and we made it home safely! I know my story was long! It really was the worst flight experience I have ever had. I'm terrified to drive in a foreign country, but honestly I would choose that over a plane. I asked so many questions prior to my flight, and I called over and over again to make sure to talk to different people. No matter how many answers I got (which were all the same) they were all wrong answers in the end... I wish you luck in making your decisions! If you have any other questions about my experience please let me know!