That's not exactly true anymore (as of iOS 11). Airplane mode will definitely stop your cellular radio from transmitting, but it is possible to still have WiFi and Bluetooth enabled while Airplane mode is active - i.e. turn on Airplane mode, then tap on the WiFi and Bluetooth buttons in the iOS Control Center to activate each. You'll see that Airplane mode is still active but you will be able to use WiFi and bluetooth connections normally. Furthermore, the *next* time you turn on Airplane mode, your iPhone will remember your previous settings and leave WiFi/Bluetooth enabled.
Apple changed how Airplane Mode works on your iPhone and iPad in iOS 11 that could be a little confusing at first.
www.macobserver.com
So yes, by default it will kill WiFi and Bluetooth. But if you then enable them while Airplane mode is active, it will remember those settings and keep them active the next time you turn on Airplane mode.