Just received the bag. The material seems very strong. A reviewer on another site mentioned that the only thing missing is a cushioned shoulder strap, so what I plan to do is use the removable velcro cushions that came with my daughter's infant carseat and put them on the straps so that my shoulders won't hurt. Haven't used it yet but plan to take it on a plane real soon, I'm just happy that the booster seat is so awesome and that it folds.
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br /Update: didn't need the cushions because it's pretty light anyway. carseat fits well, it protects the seat well when you check it at the airport.

This bag has decent construction and fits the booster seat well, but that's about it. For air travel, it's better than nothing, but also has some disadvantages. It doesn't do anything more than cover the seat--there's no foam padding or anything like that to provide extra protection for the seat against damage caused in baggage handling. (But what do you expect for around $20, I guess?) More importantly, the strap is not removable, and there's no way to secure it to the bag so that it doesn't flap around. This greatly increases the chance of the bag (and seat inside) getting lost, damaged, or delayed during airport baggage handling, as loose straps can get caught in the automatic baggage handling machinery. Be sure to identify the bag as containing a car seat when checking in at the airport, as most major airlines will have a separate handling procedure for car seats that might spare you the inconvenience of a damaged/lost bag and seat.

The bag fits the car seat nicely, only wished it had some shoulder pads for easier travel... A little on the thin side, but for the money it is OK.