how to on off airplane mode ionic 3
You can’t. At least in IOS the access to change the airplane mode is restricted and it does no have any public API, so a plugin to do it can’t to be developed. And if you use some kind of private API, the app will be rejected by the AppStore when you publish it.
Take a look on these:
https://developer.apple.com/documentation/bundleresources/entitlements
Let us know what are you trying to achieve, maybe there is a workaround to get it done.