This is my 2nd purchase. Bought the 1st one in 2016. I absolutely love the sturdiness and mostly the maneuverability of this carrier. Getting older, can't lift carriers anymore and have 6 cats none under 10 lbs and one over 20 to take to vet regularly. This has made it soo much easier to get them in a carrier and for me to carry. Plus I can lower a flap just a little to get my hand in and pet them when going to the vet. I like the openness and storage capacity also. The large one is roomy enough but I not for them to stand up in. Don't think they could. No matter. I bought it for ease of use for vet trips only and for that it works perfectly, though it is a little pricey. Whatever. Don't care as it does exactly what I wanted it to do.

This is one of the best carriers you can get if you are traveling with your small pet. I have used this carrier to transport my show dogs (Chihuahuas) many times on flights and it always fits under the seat. It's also held up for years. I have transported a whole litter to the vet in this many times. It can be buckled into the car seat for safety. I also use it when taking only one dog to shows for the convenience of it. Some of these other reviews from people apparently don't understand how to use it. The handle is located in a compartment on the side, in case the bag is checked (without animals). It WILL break if you don't take it off when checking it. It has be attached when using it and detached for storage or for placing it under a small seat of a plane. There is plenty of ventilation if you open all sides as 3/4 of the sides completely roll up for open ventilation, but can be rolled down and zipped for complete privacy. The directions explain how to use it. I have had to completely hose this carrier out due to puppy accidents and it has held up well. It is very discrete for airports or events and my favorite carrier.

It seems very sturdy and should be great. I'll be flying on Allegiant on Monday so I'll know then how it is under the seat. I actually did some alterations so I don't have to bother taking out the floor panel for it to fit under the seat. My dog is small enough that it isn't a problem with it only being the width without that panel. I cut out a strong piece of cardboard and contact papered it to fit within the bottom without the extra width that the floor panel gives it. I then put velcro on the back and put the floor panel there so it would stay when I turned the stroller on it's side. I also used velcro to keep the pad in place on that panel and put another one on the contact papered cardboard panel. We'll see how all that works on Monday! I'll give you an update.

March 30: The flight went good but there were a couple hiccups. This carrier doesn't fit under the window seat of the M80 plane I flew on. Luckily I was able to trade seats. It fits fine under the middle and isle seats. The only problem was the width under the window seat.

The other hiccup was my fault. My poor dog got tossed around a bit while I tried to figure how to maneuver the carrier to actually get it under the seat. I had to turn it on edge to be able to slide it under the seat.

As far as traveling thru the airport, it was a dream! Even tho my dog doesn't weigh that much, the long walks thru some airports can be a challenge. It was such a pleasure this time! And because of the wheel design, it's very easy to maneuver.

Oh, and the few alterations I made worked out perfect. And because there was more padding on two sides and his blanket inside, his experience while I was tossing him about trying to get the carrier under the seat wasn't as bad as it could have been!

I love that you can drop down the sides to cover the screens but also that there are screens for ventilation when needed. The one side that is the pouch to carry stuff in is great. Just don't put bulky stuff in it. That's the side your pet will be laying on under the seat!

I love this carrier!

Update on airline travel. Normally I have no trouble fitting this carrier under the seat but it does depend on the way the seats are configured. One time it wouldn't fit all the way under because there was a low bar under the seat making it too low for the carrier.

Update 12/21/2018.

Well, Allegiant has new planes and the area under the middle seat isn't big enough for this carrier. I'm very sad. Heck, when I sit in the seat, my knees hit the seat in front of me! They added more seats making the area for each seat smaller. Not good for people or pets. This isn't a negative review for the carrier. I still love it. I just wanted to let people know that it might not fit on some planes.

Pro: Shoulder didn't hurt while lugging around my 6lbs yorkie around the airports like all of my shoulder-mounted soft-walled bags. This is VERY important to me, so it fulfilled its purpose.
Cons: Barely fit under the seat for all four Delta planes I rode on during my trip.

Instead of my feet being like:
| |
They were like:
| _
or:
\ /
or once it had to be more like:
_ _

Got hassled once by the flight attendant, but it was ok because I was at the window seat and 'wasn't blocking anyone'. The bag also has to be laid on its side. Thankfully my dog is well-trained and does not bark nor does he complain, but I'm sure it wasn't the most comfortable feeling to be tipped over several times while I'm sweating balls trying to maneuver the thing onto its side (much harder than it sounds when crammed into economy). So, all in all, it's doable, but I will probably have to come up with some sort of removable-caster workaround before travelling with it again because as far as I could tell, it was the wheels that were getting caught in one of those stupid rails underneath the seats.

I have a 25 lb cat, it was perfect for him, but he could only lay down, he couldn't stand or turn around in it, but the carrier has a window where he could stick out his head, he's so large he couldn't escape, plus I zipped it only for his head to fit. It's lightweight, which I like because I could put in my car easily. The plastic carriers and the wheels add weight which makes them too heavy by the time u put the cat in this particular type carrier your lifting 50 lbs. I use it to take him to the vet, only short distances so it works for me, I won't use it for long trips. However the carrier is of high quality and made very well. Perhaps I should've ordered the extra large carrier for better comfort.