Application.internetReachability value does not change to "NotReachable" when the airplane mode is enabled from the status bar. However sending the application to the background by pressing the home button or by opening the recent applications overlay by pressing the app switcher button and then resuming the application properly detects the internet reachability change. Contrarily when the airplane mode is disabled from the status bar (WiFi is enabled automatically), then the internet reachability change is detected instantly and the "ReachableViaLocalAreaNetwork" status is returned.

Reproduced on:
Google Nexus 5 with Android 4.4.2

Reproduced with:
Unity Version 4.5.0f4 (e54dddc56c0d)