This past summer I packed mine in an electric bike box (free from electric bike rental store) - much bigger and sturdier than regular bike boxes. Checked it with connecting flight on way out, shipped home in another electric bike box. Front wheel, handlebars, seat, pedals, rear derailleur all removed and bike slipped into box quite nicely with front and rear racks and fenders installed so minimal disassembly and reassembly required. Both boxes held up very well. I've saved the return box for the next time.
Note that even TSA couldn't muck things up.