Previously, I have owned a Sherpa carrier and have used it only when necessary for hurricane evacuation, etc. It is huge, and fit both pets I once had. The Sherpa is great if you have a larger pet and no real carry-ons. (I believe it's the largest carrier that is allowed on the major airlines; the dimensions are bigger than what is stated on their websites, but Sherpa is the only carrier that is mentioned as bigger yet an allowed exception.)I now have a kitten and I wanted something that would be discreet and fit with my rollerboard suitcase.The Atom is a perfect size for my kitten. She can sit or stretch out with no problem. Right now, she's only 2.5 pounds. To compare, I put my sister's 11 pound cat in the carrier. She fit snugly. Although she couldn't sit up, she was able to stretch out slightly and seemed comfortable. I think it would be great for flights 3 hours or less.When I received the carrier, I put it on the floor and placed some toys in it to get my kitty used to it. She wandered into it and was even found napping at one point.The Atom slipped easily onto the handle of my roll-aboard. In this position, I liked how my pet was raised nearer to my eye, which allowed me to be very aware of how she was doing.I purchased the black Atom, and it blended well with my other black luggage. The zippers seem sturdy and the bag feels well-constructed. There is a clip on either side of this bag which can be hooked onto a seatbelt. This is a great feature, in addition to the handle sleeve, for seamless transfers between car, luggage, and plane.Cons: Pockets are nice, but they close only with a small velcro tab. Things may easily fall out. The shoulder strap is nice, but there is no way to disconect it. For my purposes, I used the handle slide when walking through the terminal and I used the handle located on the top of the carrier to carry the bag. The shoulder strap only got in the way.I would definitely suggest this carrier to others who have a small pet.