I bought mine at Dicks.
It has a big sticker saying it's approved right on the label.
Just to be safe I peeled the "approved" label off of the outside & stuck it back on the inside. That way if I'm ever asked (which has never happened) I just tell the checkers to lift the top foam & look under it for the label.
This is nowhere as big a deal as some would have you believe BTW just relax& get a case that has a sticker saying it is "airline approved" or something similar & you'll be fine.