Depending on the airline, you can bring it as a piece of checked luggage. Be very clear and careful when discussing this with the airline so as to not have any unforeseen problems. I took a bike back to American and was great on the flights from Chengdu to Beijing to Chicago (all on Hainan), but the domestic flight home from Chicago (on United…) was a nightmare and ended up costing me like $150 and they damaged the bike…
Don’t skimp on the packaging for the bike.