Airplane Mode on iPhone doesn't turns off Bluetooth on iOS 13
iOS updates always have more than it meets the eye. There are minor features that don’t make it to the stage, or even the features page, but are pretty handy for everyday usage. One of such minor improvement is in the Airplane Mode on iOS 13.
On iOS 13, Airplane Mode disables all radios except Bluetooth on your iPhone and iPad. Apple updated its support page earlier today to highlight this change in iOS 13.
With iOS 13 and iPadOS, when you turn on Airplane Mode, it turns off all radios except for Bluetooth. If you turn off Bluetooth while you’re in Airplane Mode, your device will remember the next time you turn on Airplane Mode.
This only affects users who have never turned on Bluetooth while using Airplane Mode on their iPhone. Because if you did, your iPhone already remembers that and doesn’t turns off Bluetooth anyway when you enable Airplane Mode.