I just successfully completed my first trip with the Studibag, traveling from Minneapolis to Denver, on 12/20/22-12/28/22. I will try to keep this as concise and organized as I can, but I have a lot to say, so bare with me.SIZINGI ordered 6 other bags on Amazon and none of them came close to being an appropriate size for my dog, and I wouldn't seriously considering ever trying to squeeze him into any of the others I ordered. If you are reading this review, you are likely in a similar position. My American Eskimo is 25lbs, about 22 inches from the back of his neck down to the base of his tail, and longggg legs. At first I thought the XL might even be too small for him, but it was going to be our last chance at getting him to fly in-cabin with me, so we went with this one to practice in before our trip.TRAININGTraining your dog to be comfortable in this will be very important, especially if they are not crate-trained. I have an anxious puppy mill rescue who was crate-trained when I adopted him 3 years ago, but after 6 months of having him, he started sleeping in my bed and we never turned back. He was very hesitant to get into this bag. Slowly over the course of a month, I started playing games with the Sturdibag. Every night, I would say "crate!" and throw a handful of cheese into the Sturdibag, which he would run into and take several minutes to explore and get every last piece of cheese. After doing this for a few weeks, I started giving him some long-lasting chews and gently blocking him from the leaving the bag. Once he became content with laying in the bag and chewing his treat, I zipped up the bag and stayed nearby. Leaving him in it for 10 minutes at first, then trying a little longer.The next milestone in training was the carrying part. The first time I picked up the bag my dog was horrified, and desperately tried to climb out the little window at the top. He eventually was able to feel secure by sitting in the bag with his head up through the hole. To practice, I would carry him around the house, stopping at various spots to give him treats.NOTE: Since I have an anxious dog, I asked the vet if they would prescribe something for him to help with anxiety. They gave us a medication called Sileo, which is meant for noise aversion in dogs, and it worked great for us.Our last step in training was to do a dry run at the airport a few days before our actual trip. I gave my dog his first dose of Sileo, and he went to the airport. I transported him outside of the carrier and allowed him to walkaround first. I walked him around outside for a bit, to get him used to the smells and let him pee on a few things. Then we walked inside and did a lap indoors (still outside of the carrier.)TECHNICALLY most airports state that your dog must ALWAYS be in the carrier, but I did a lot of research, and it seems like you are able to walk your dog around in most airports just fine and nobody is going to say anything.So, after we walked around inside, I found a quiet corner and set down his carrier. He was feeling a little out of sorts likely from the new location and the Sileo medication, so he went right into the bag as soon as I set it down. At that moment I knew all our training was worth it because he saw his Sturdibag as a safe place to go when he felt uncertain. I picked him up in the Sturdibag and walked around a bit more before going home from our practice session at the airport.NOTE: I have all sorts of back problems and carrying my 25lb in the Sturdibag is no easy task, but I was surprised at how comfortable and manageable it was overall. The lightweight particle board at the bottom of the bag will make your dog feel secure as well.OUR FIRST FLIGHTI did everything in my power to prepare for flying with him. There are lots of YouTube videos and blogs out there, so I recommend you watch/read as much as you can as well. The day of our first flight, we arrived at the airport three hours early. I flew with Delta, which normally has a very slick check-in experience on their app. When you fly with a pet on Delta, you want to call ahead as soon as possible and reserve your dog on the flight, as they only allow so many animals. You will pay a $95 fee each way, on the day of your flight, but you still need to reserve their spot. At the time of the phone call for the reservation, ask them for the dimensions of the under-seat area for EACH plane you will be on, and write this information down.IMPORTANT NOTE: MAKE SURE YOU GET YOUR BOARDING PASS PRINTED WHEN THE TICKETING AGENT GIVES YOU A RECEIPT FOR YOUR DOG. If you have an animal on your reservation, you cannot use your Delta app to check in and need to speak to an agent.The first issue we ran into, was that I checked in my dog and other checked bag just fine at the Delta counter, but then the agent did not print me my boarding pass, and like I mentioned above, you cannot access your boarding pass on the Delta app when flying with a pet, so you will NEED that printed boarding pass. We had to get back into the line with the ticket agents a second time after realizing we never got my boarding pass, and this resulted in us being way later to our gate than I wanted to be.SECURITYSecurity was a breeze. Highly recommend getting TSA Pre-check or a CLEAR membership to make this step easier. I couldn’t get TSA Pre-Check in time, but I did sign up for a free trial of CLEAR, which was really helpful. We got to the front of the security line quickly with CLEAR. Once you get to security, your dog will come out of the carrier and your carrier will need to be sent through the x-ray. I purchased a TSA-compliant leash and collar from Etsy (ImaginedByKristi) which was helpful because then I didn’t need to remove his collar/leash to go through the detector. It was a bit stressful trying to take all my electronics, snacks, shoes, etc off and keep it all together while managing my dog in the security line. But my dog and I walked through the security arch thing (not the main one where you lift your arms up, but the older tech one they usually have on the side) and all they did was swab my palms.ONWARD TO THE GATELike I mentioned before, nobody in the airport is probably going to say anything to you about having your dog out now, so you can let them walk a bit in between security and getting to your gate. You may want to consider them keeping them in the carrier if you’re stopping for a coffee or whatever, but otherwise you’re probably fine if they are quiet and well-behaved.BOARDINGDue to my own lack of time management skills and not getting an official “boarding time” updated on the Delta app for our first flight, I was one of the last ones to board our first flight. This was NOT ideal, as I had intentionally paid for early boarding and picked a window seat, based on other reviews people have written on this page. I rushed to the gate, with my dog in the bag and over my shoulder. The gate person is your final and most difficult checkpoint with getting your dog on the plane. The gate lady looked at my bag and said, “I think that’s going to be too big to store under your seat.” I responded (out of breath from running to the gate), “No trust me it will, we have been practicing and I took all the appropriate measurements.” She didn’t want to, but she let me on!!! This was stressful because I had a window seat and the two seats next to me already had people seated in them, so it was an awkward shuffle to have those people get up, set my dog in my seat, put my backpack up ahead, then get to my seat, adjust my dog on my floor and finally seat and down. Since I was the last one on the plane, it was way too difficult to remove the spines from the carrier, so I just shoved it under as is, the best I could. Fortunately, I had the Comfort + seats on Delta, because I still had room for my legs, even with his bag halfway sticking out.SECOND FLIGHTThe process of checking in and getting through security at the Denver airport was pretty similar and a little smoother than our first flight since I got my boarding pass printed this time. However, when we showed up to our gate (a few minutes after Comfort + had been called to board), the gate agent took one look at my bag and said, “That’s too big to fly, I’m not letting you on.” Now granted, it was the 28th, and I’m sure this woman had had a really difficult work week. But she would not listen to a single word I had to say. I had all the dimensions written down of what I had been provided for the under seat on the plane, I had dimensions of the bag, I had photos of others using the bag, I had photos of us using the bag on our flight there. That didn’t matter to her at all. She just ignored me when I would try to politely mention any of this to her, and she kept scanning people onto the plane while ignoring me as I stood off to the side. I did start to panic a bit, but I kept my cool.Finally, I asked her, “Can I please speak to a manager?” She looked stunned that I would request such a thing and continued ignoring me and scanning other people in, but then eventually she called a manager over. The “manager” eventually comes up, who frankly looked like the manager of the ground crew, as he was wearing a hi-vis vest. He looked down at the bag and asked to see my dog turn around. I was nervous my dog was picking up on my nervousness and might not comply, but fortunately I had treats in the bag pocket of the bag, so I shook the treat pocket and he easily turned around in the bag. The manager, who I could tell was a dog person, seemed satisfied and said he would tell the gate agent to let us board. This entire interaction was really interesting because the gate agent seemed concerned that the bag was too big, where the manager was mostly concerned about the dog having enough room. I get back in line, and I hear this gate agent still arguing with the manager that I shouldn’t be let on. He reassured her several times that it was fine. She finally scans my boarding pass, and I still keep my cool and thank her. But as I’m walking away, I hear her mumble to the manager about how a flight attendant will probably end up kicking us off because of the big bag. I hated how close of a call this was, but we made it! Again, I had the window seat and the people in the other two seats were already seated so it was an awkward shuffle to get myself and my dog situated in our window seat. I had removed the spines while waiting for the manager, so I was able to fit the bag a bit more under the seat this time.DURING THE FLIGHTMy dog did pretty good during the flight. He just slept and seemed pretty comfortable. I think the second flight the bag collapsed on him a bit and he didn’t love that, so I think next time, I would remove the first 2/3 spines that give the bag the circle shape, and leave the one in that creates the opening entrance. I also kept in the two vertical spines that go lengthwise on the top of the bag. NOTE: it was really hard to find a place to store the spines during the flight. I got the window seat because people in these reviews mentioned putting the extra pieces on the side of the plane by the window, but the spines are LONG, and I was scared they would slide up and down the plane if I rested them down on the floor. I tried tucking them into the pocket in the seat in front of my me but curling them into a circle, but it they popped out a few times (fortunately the person next to me was sleeping when this happened otherwise they could have gotten an alarming poke from one of these spines). The only solution I can think of for storing these, is to try and curl them into a circular shape the best you can, and store them in a backpack with the zipper closed so they can’t pop out.Overall, my anxious guy did a really good job on both flights, and was only a little nervous on take off. But as long as he could stick his face through the top hole and touch my legs, he seems assured and fine.SUMMARYThis bag is probably your only option if trying to fly with a big-small dog. You are taking a risk with the XL bag because some agents may refuse to let you board, so be prepared with evidence in case you need to speak to a manager (I think next time I will bring a folder with printed images of dimensions and other product reviews, evidence we’ve flown with it already, etc.) Just remember to keep your cool when speaking with anyone and always be polite, they are just trying to do their job.Good luck!