HELLO!!! Ignorant IT people. It's really quite simple...

If you have a system or network that either contains information you don't want leaked out,
OR (As in this case)
The system/network that controls a critical operation.

YOU DON'T CONNECT THE FLIPPIN' THING TO THE INTERNET!
There are other methods for systems to interact should they need to. Like Encrypted land line? Radio? WAN using the flipping power lines for data transmission? HELLO!!! WAKE UP!!!

I don't care what OS it's running. None of them are bullet proof.

*Flight attendant walks into the seating area*

"Excuse me everyone, is there anyone present who has computer hacking or security skills?"

(Scene taken from a rejected Die Hard 2 script)

Now that is scary!
"Really, would you get on an airplane knowing its flight control system runs under Windows?"

MAC would be you can't turn left if you hold the steering wheel with your hands at 10 and 2.

Really, would you get on an airplane knowing its flight control system runs under Windows?