Fit under the seat in a 737-700/800/MAX8 plane (see photos). Our female Italian Greyhound puppy is 4 months old and 70% of her full size (6.5lbs now) and she had no problem in this carrier, happily stretched out to snooze on her side. I bought this bag for its top quality construction ... (think TUMI brand luggage!) and didn’t think about this extra benefit until I travelled with it: I booked our hotel forgetting to check their pet policy. Thankfully our girl was always quiet and the black mesh kept anyone from knowing we had a dog. Worked nice in the truck too because the supportive floor bottom was nicer for her to rest on than our laps and shaded her from harsh sunlight coming through the windows. Even the airline gate agent didn’t know we had a puppy inside (man we could have saved the $95 each way on Southwest! - LOL - don’t try it because Honesty is the best (God’s Policy) and Murphy’s law will wreck your trip). Side zip pocket is just right to store a leash and puppy pad. The other side dual zip section let’s you put the bag on top of luggage having a pull handle. My pup wanted to destroy the plush floor liner thinking it another plushy toy so I threw in a blanket instead - simple. The bag feels like it is made of water resistant, woven ballistic nylon. Truly a worthy investment and will last a long time.Update Jan2919 my girl is just shy of 10 pounds and still fit into & traveled in it just fine. She cried a bit and I thought it was a kindness to gently slip my fingers inside to reassure her. Well after about 4 times decided to change that around and not reward the behavior. A small, gentle kick to the side of her carrier quickly nipped that behavior in the bud after about 4 times. And yes I love her so very much. Cheers