My husband and I recently traveled for the holidays and purchased the Sherpa Original Deluxe carrier in a medium for our dog. For reference, our dog is 11 inches in height and weighs 7 lbs. With Sherpa, there is a "Guaranteed On-Board" (GOB) with this carrier. Once you have purchased the carrier, you follow the directions included with the Sherpa's instructions. I suggest you find out if your airline is included with Sherpa's GOB before purchasing the Sherpa by going to their website www.flygob.com. Some airlines do not approve specific Sherpa carriers (some only approve the Deluxe and not the others) and some do not include all of the carrier sizes.We flew Southwest Airlines to and from our destination including the connecting flights. Southwest Airlines is apart of Sherpa's GOB; however, Southwest Airlines only approves the small Sherpa and not the medium or the large. We purchased the medium anyways so that our dog had more room. There were no issues with the size of our Sherpa (medium) and Southwest. They didn't look at it or inspect it. The middle seats on Southwest have more leg room than the aisle and window seats, which is where my husband sat with the carrier. During take off and landing, the carrier has to be under the seat, but in the air we were allowed to have the Sherpa in our lap on all flights with no issues.As far as the carrier itself, the medium was a good size for our 7 lb Papillon. He was able to lie down comfortably with the top closed and was able to stand with his head poking out. The carrier was not that heavy while walking with him in it, maybe around 10lbs. There is also a pocket that zips on the back of the Sherpa where we kept his leash, a collapsible water bowl, and some treats. Our dog also had no issues with the Sherpa, but I also prepared him by training him with the Sherpa before we traveled. I would carry him in the Sherpa around our house and reward him with treats if he went inside of it, sat in it, or would lie down in it.I have included some photos with this review for reference:Photo #1: The carrier itself, which has a faux lambskin liner.Photo #2: The rear pocket that zips, which we kept a leash, a collapsible water bowel, and a bag of treats in.Photo #3: Our dog standing in the Sherpa. For reference, he is 11 inches in height and 7lbs.Photo #4: Our dog sitting in the Sherpa.Photo #5: Our dog laying down in the Sherpa.Photo #6: My husband sitting in the middle seat on Southwest Airlines with the Sherpa underneath the seat in front of him during take off. The Sherpa fit fine with no issues and my husband was not uncomfortable.Photo #7: My husband sitting in the middle seat on Southwest Airlines during landing. We zipped the top flap up just enough where our dog could poke his head out and see us.Photo #8: During the flight, we were able to have the Sherpa in our laps so that we could comfort him. This was not uncomfortable and our dog did fine.Photo #8: Our dog slept in the Sherpa comfortably with the Sherpa in our laps during the flight.Overall, this was a great carrier to travel with, our dog was as comfortable as he could be all things considered, and I would highly recommend it considering their "Guaranteed On-Board." Be sure to check their website first before you purchase to ensure that your airline is apart of Sherpa's "Guaranteed On-Board" at www.flygob.com.