Joe Simpson put this rad little guide together on how to travel with your bike & keep in under 23kg. You can check it out here: chuckitinbmx.tumblr.com
I also did a post a few years back recommending using a golf bag. I’m not sure if it really matters these days but golf bags used to be the favourite for travelling BMXers. The reason being is to avoid any extra charges, for some retarded reason air lines will often charge for extra bags but let golf clubs on for free (which is bullshit).. so packing your bike into a golf bag is a nice little loop hole to avoid any extra charges.
Definitely check out Joe’s guide, it has some good pointers for sure.