Snoozer Roll Around Travel Dog Carrier Backpack 4-in-1- Rolling Backpack Pet Carrier with Wheels for Cats & Dogs, Pet Stroller, Travel Bag for Pets Up to 15 Lbs - Black, Medium

Size: LargeDog weight: 15 lbsHeight/length: 14"/17"Airline flew on: United (airbus and Boeing 737-700)Seats: upgraded to economy plus both timesOK overall I have to say I love the Snoozer carrier! I only dropped one star for durability reasons, especially considering it's such an expensive purchase. I've had mine less than a month and the metal framing already poked through the bottom (last photo attached), not a huge deal, I am still using it of course but it's kind of annoying to have happened so early and it's not like my dog is over the weight limit --he's only 15 lbs. (June 2018 update: contacted company about the wire frame and they sent a warranty replacement so returned the star)Anyway, that's the only bad thing the rest is all praise! I use it all the time in the car now but my original reason for purchase was for a flight to California (about 3.5 hrs) and the reviews with detail about the airlines really helped me so I broke down my specific airline/plane details above so it's clear what this carrier fit on. Also attached plenty of photos! I choose the large because my pup has long legs so I was worried he'd be too cramped in the medium (1st photo shows size comparison for large sized carrier vs. standard backpack). Glad I did because when I got it I knew instantly he wouldn't even have gone into a medium willingly. He fits upright perfectly with the zipper closed, and when laid down he can still move around to change positions if needed. I was nervous about the large for flights due to some other comments so I did upgrade my seat both ways just in case, on the airbus I had tons of room so probably wasn't needed (3rd and 4th photo) but on the 737 I am so glad I did cause that one was tighter (5th photo). I had window seats both times, by the looks of it would have been fine in middle or window for both planes, would not recommend the aisle they tend to have smaller under seat areas. Recommend talking to the flight attendants when you get there, they let me pre board both flights so that made it easier to get the bottom panel off and get him situated under the seat, sometimes he spins around funny and is kind of tangled in the little leash/restraint.I purchased the Snoozer one week ahead of the flight and practiced with it (with lots of treats!) all week (2nd photo), by the time we had the real deal he was used to it-- the transition from upright to slanted when rolling is what took the longest so take your time getting them used to it stationary with treats before trying to move around (and keep it zipped when moving for first time! Mine tried to jump out even with the restraint attached to his harness). First flight I kept it zipped when rolling through the airport, but by the second flight he was an old pro so I left it open and it had his head popped out while rolling through the airport.Only thing I wish I did differently for the smaller plane was have a cooling mat. Circulation on the airbus was fine but on the 737 he ran a little hot. I pulled his carrier forward and had the top open most of the flight so he could poke his head up to cool off.This was our first flight together and all in all it was a great experience! Only was questioned by two people about the carrier on the way home actually, but once I said I've flown with it and it fits (bottom comes off) there was no problem. Security was easy too; you just carry your pup through the old school metal detector and they check your hands. Make sure to take your treats out of the carrier and run them through separately, on way home that got my bag flagged for inspection.Hope this info helps other travelers with furry friends! If your dog is small enough go with the medium but if you have to use a large it at least fits in some planes! Just need to do a little research, I will definitely fly with my guy again and will be using the Snoozer!!

UPDATE 6/28/2016Since buying this 2 years ago, have used it on several domestic flights mainly with Southwest, and I can confirm that the large one does fit under their seats. I have the Large one. Make sure your particular dog fits in the bag, though. At check in, if they question you (only happened to me once) you can show them that it is collapsible once the removable base is off. When walking thru airplane isle, may be easier & quicker to just carry it, rather than roll it. As for durability, material has endured, without a scratch. Just be careful that bottom plate is attached correctly when moving around. Otherwise, it will be damaged.So convenient and versatile. From backpack, to rolling, to under seat.Very convenient carrier for medium breeds, up to 9,5 kg ( +/- 20 lbs.) My dog is a Miniature Schnauzer, with a large frame for his breed and he was relatively easily transported thru airports, gates, on board, etc. Most of the time I had the carrier flat in waiting areas, and he conformed just fine, no troubles. He was comfortable. If it was possible, I did let him have some breathing space and allowed him to have his head out and watch the world go by. Having said that, my particular pet is quite easy-going with a very predictable temperament. Non-aggressive and sociable and very physically flexible. And not a whiner.I did fly with Air Canada, (relocating from south Europe to US) due to the maximum weight allowances for pets, (10 kg) and selected Premium Economy, from Europe to Toronto. In an aisle seat, the carrier was not easily tucked under the front seat, however, even with taking out the removable base. I had to give him to my son, who was seating across the aisle in a window seat, so that it could squeeze in with more room to spare. I have to say that he was seated next to a very kind man, who did not mind relinquishing some of his leg room.Flight from Toronto to the US, on a much smaller aircraft, ironically the leg room was much more spacious in regular Economy. More room to spare, so you might take that into account. The difference being not on the overall dimensions, but in the structure of the premium economy seats. The legs of the front seat were much closer together, leaving less room available.That said, the crew was not at all bothered by the minor trouble when boarding. They even offered water for him. But again, no one even realized that there was a dog on board. We were able to very discreetly pet him to reassure him, feed him, etc and he laid flat mostly sleeping the whole 10 hour flight.Carrying it throughout the terminals, you do need to be careful switching positions from flat to standing, if you have a heavier dog, as you can lose the balance if you do not control your movements. Steady and slow when switching. And my dog, as said before is a tall and long dog for his breed, but very lean and flexible.The construction material is very durable, just make sure you put some kind of blanket for warmth and padding. The handle is sturdy as well.All in all, a really good purchase worth the money (and I had to pay a high delivery charge, on top) because apart from being a breed that is instinctively highly anxious during times of separation, he does have a heart valve dysfunction that causes rapid palpitations and I did not want to put him through the ordeal of cargo shipment if I had a choice, especially during the summertime. Highly recommended..