I believe it's 40lbs but I am not 100% on that. However, AA never really weighs these ever. What they do care more about is size, so be sure it fits the AA sizer requirements. So that being said, you especially don't want to pack it so full it's bulging at the seams like many people do. You are supposed to be able to lift it into the bin yourself, so as long as you can lift it, you will be fine. Now if you pack it full somehow to 100 lbs and are visibly struggling lifting it up to the bin, then you may have the attention of a FA.