Alisha Gambhir writes in, noting that her MacBook Pro suddenly reported that it had no Wi-Fi hardware installed. This is odd because, as you know, all Mac laptops (and nearly every Mac made for several years) includes a Wi-Fi adapter.
There are two ways you can wind up with an x in the Wi-Fi menu’s icon. One is what’s happened to Alisha and other folks who have posted about this problem over a few years; the other is when the adapter has been disabled via the Network system preferences pane. If you click the Wi-Fi icon and the dropdown menu reads “Wi-Fi: Not Configured” then the adapter has been disabled.