Bluetooth and Wi-Fi can be set to stay on when Airplane Mode is activated in iOS 11
Now, let's say that you are using Bluetooth to pair your Apple Watch with your iPhone. Using Airplane Mode would traditionally eliminate the Bluetooth connection and your timepiece would no longer receive data from your phone. You would have to manually turn on Bluetooth and Wi-Fi to use either or both without a connection to your carrier.
With iOS 11, this is going to change. Users will be able to set Bluetooth and Wi-Fi to remain open in Airplane Mode. That means even with Airplane Mode on, Bluetooth connected accessories like AirPods and Apple Watch will still be connected to the iPhone.
The 2017 iPhone models will come with iOS 11 pre-installed when they launch later this year.