How is it possible to listen to FM radio while a phone is on airplane mode? My phone was on airplane mode, i forgot to turn it off then i decided to listen to Fm radio. It worked really well. I still wonder how airplane mode works. Shouldn't it be disabled first cause i just read that some wireless devices work while  on airplane mode.
Air plane mode disables all transmitters as these are creating the strongest radio waves that exit your Smartphone.

For some services like mobile network, WiFi and Bluetooth disabling only the transmitter without also disabling the receiver does not make sense, therefore both services are completely disabled.

The fm receiver however only receives the fm frequency and therefore does not have to be disabled in air plane mode. The same holds for GPS.

Note: Even disabling all explicit transmitters of a Smartphone some implicit transmitters of radio waves may still be active, e.g. the CPU and other electronic components can emit radio waves. However those radio waves are a lot weaker than e.g. a WiFi signal.