Also keep in mind that wifi is allowed on airplanes so you just need to turn it off for take off and landing but thereafter you can use wifi and most planes now have wifi access.
WiFi is allowed over 10,000 ft as most commercial aircraft now, short of some regional jets have WiFi available. Bluetooth I would imagine is somewhat harmless (I think it all is actually, but.....whatever).
Airplane mode is for the radio in a phone/(or tablet using data services), or other device using cellular radio that airlines claim will have an effect on the navigational equipment of the aircraft. Playbooks don't have this, so there really is no need for an "airplane" mode.
If you're worried about it, just turn of WiFi and Bluetooth, it takes two seconds by clicking the icons on top of the home screen.