Hi
It is possible for turning on Airplane Mode to be mirrored between devices, but the same does not apply for turning off Airplane Mode, which must be done separately on each.
To change the setting for mirroring the turning on of Airplane Mode:
On your iPhone, in the Watch app, go to: My Watch (tab) > General > Airplane Mode - enable or disable Mirror iPhone, as preferred.
To turn on / off Airplane Mode on your Apple Watch:
If your Apple Watch is locked by a passcode and cannot be unlocked via the normal process, then follow these steps to erase your Apple Watch and re-pair it with your iPhone:
- Connect your Apple Watch to its charging cable, connected to power.
- Whilst keeping the Apple Watch on the charger and connected to power:
- Press and hold the side button until you see the Power Off slider.
- Press firmly on Power Off (do not try to slide it - just press down more firmly than a normal tap), release your finger and then tap on Erase all content and settings and confirm when prompted.
- Re-pair the watch using the Watch app on your iPhone, choosing to Restore from Backup if offered the option.
More information:
Set up your Apple Watch - Apple Support
If you forgot the passcode for your Apple Watch - Apple Support