Board Thread:Battle Nations Discussion/@comment-9595550-20130515204129/@comment-4632427-20130611203636

"Airplane mode" means "turn all internet connections off." It's for when you want to use a device on an airplane, and all forms of radio - wifi, cell phone, etc - are illegal to use due to the risk of them interfering with the plane's instruments and causing a crash.

BN is an online game, so it won't work if you're not online. There's no real way around needing airplane mode to be off to play it.