Yep, the easy way is to plastic wrap it and check it in as a large/bulky items. His way isn't so easy and involves it sitting on a seat next to him (with the seat belt on). Lol. I travel with guns all the time, sometimes long gun cases, and ammunition and it's surprising to see what else goes on planes, some things the passengers would never expect. A BMX bike is the least of it.
I'll probably do a post or two when they're here and may get a chance to photograph the bike as I'll be the one picking them up at the airport. I'll get back to you.