I definitely understand the importance of being able to reach 911 when most needed. When it comes to Wi-Fi Calling, in order to offer voice service over the internet, Verizon is required by the FCC to support 911 calls and collect a registered location to enable the service. By registering an address, you’re providing information that determines how your 911 call will be routed. This information will be provided to emergency services if you’re unable to report your physical location.
When using Wi-Fi Calling, 911 calls will always try cellular service in the local market first, even when the device is in Airplane Mode or cellular service is off. If cellular service isn't available and the user has set up Wi-Fi Calling, the 911 call will route using the registered address.
Here are more details about Wi-Fi Calling- Emergency Address https://www.verizonwireless.com/support/wifi-calling-faqs/