What a hilariously misleading headline.
Misleading external radio signals is not "hacking airliner systems". That's providing bad inputs to aircraft systems.
If someone actually manages to hack into the avionics, in the conventional sense of gaining direct control of the system on board the aircraft, all bets are off, and you won't see pilots shrugging it off. That's a lot harder to achieve of course, and fortunately hasn't happened as far as we know. Nevertheless, the risk is always there with networked aircraft that can speak to the internet.