Unfortunately, due to security restrictions introduced by the Android team in 4.2, there is no way to automatically enable airplane mode from an app. You always have to go into settings or long press the power button. If you have a rooted phone you might consider using https://play.google.com/store/apps/details?id=lv.id.dm.airplanemh we have support for this in Sleep. A similar hack exists for 4.3.
This is a companion discussion topic for the original entry at https://sleep.urbandroid.org/docs/faqs/airplane_mode.html