Earlier quoted context omitted.
> I click on the wireless icon and click "turn off". For that, the laptop must be on and booted. The main advantage of the hardware rfkill switch is that you can flick it to disabled before booting or waking up the laptop, so that it doesn't even try to connect before you can get to the wireless icon. (I've done that before: on a plane, want to use the laptop, which is sleeping in the bag; just flick the rfkill switc…
> For that, the laptop must be on and booted. The main advantage of the hardware rfkill switch is that you can flick it to disabled before booting or waking up the laptop, so that it doesn't even try to connect before you can get to the wireless icon. Fair point. However, planes don't require turning off wifi or bluetooth during normal flight anymore. (And even when they did, no actual harm was done either way.)
When I last flew (domestically, last year), the instruction was still that devices could only be used if they had an "airplane mode" function. Things might be different in your country. (And yes, I know normal 802.11 probe request packets won't do much interference, if any, to airplane systems. Still, it doesn't harm to flick the rfkill switch to disabled.)