I got a bike box from my LBS. It was one of the larger cardboard boxes, I think they said an e-bike had been shipped inside it. It weighed 14 pounds. My bike, with frame bag and ExtraWheel trailer all fit just fine, weighed 49 pounds. I wrapped a couple turns of paracord around each end, for ease of handling. Tie knots that can be easily untied, and don't go overboard using duck or packing tape. Airport security will open the box to see what's inside.