IT Does Fit under the United air line seats in Coach. But do not get the isle seat, it almost doesn't fit. The isle seat is not as wide. So pack to be able to stuff it under. Also it is a little long and sticks out a few inches in either the window, middle and Isle seats. It is Roomy. A couple pair of jeans, a pair of dress pants, a few pair of underwear, socks and couple of shirts. One laptop, a phone and tablet. The material seems thin, is not very stiff and the bottom doesn't have a stiff reinforcement. But I used a pair of jeans, folded them over four times to stiffen the bottom. Not sure how the material will wear yet or the zippers yet. The back straps and top handle seem strong. Have been on six trips so far. Also with the above I still had some room, it was not Over Packed/ Stuffed.