Yes, the autopilots can be turned off, but that's just a button, probably a button on the autopilot itself. Depending where the infection happens, the actual position of the yoke could be entirely ignored by the software. Or the motor controllers for the control surfaces themselves could be driving the plane, though I don't know how they could coordinate their actions and get feedback from an IMU.
Perhaps the pilots could rip out components and cut cables fast enough to prevent the plane from reaching its destination, and maybe they could tear out the affected component and limp back to a runway with what remains, but it's an entirely feasible movie plot.
But should we actually worry about either? No. The software sourcing, deployment and updating protocols at the various manufacturers of aircraft are certain to be secure. Right?
This gives us the classic reassuring response from Boeing spokeswoman Lori Gunter :
"There are places where the networks are not touching, and there are places where they are," she said.
Airplaine components tend to have shitloads of fuses for each components, any trained pilot knows how to disable the fuse for the autopilot system (or, in an extreme case, ALL fuses to kill the entire airplane).
And
https://m.youtube.com/watch?v=Uy3nXXZgqmg
TL;DR you simulate a bunch of other planes in close proximity and the auto-pilot freaks out and tries to avoid them. As the second talk explains, the pilots would definitely notice and switch autopilot off. This is why IMO it's very important to not take ultimate control away from humans in cars. I would personally never buy one of the Google (or any other) self-driving models with no controls. It already freaks me out that many cars are drive-by-wire (for the accelerator), and now even steer-by-wire: http://www.caranddriver.com/features/electric-feel-nissan-di... #noThankYouPlease
Another reason traffic spoofing wouldn't cause the aircraft to deviate is that airliners fly standard approaches and departures (STAR [1] and SID [2]) and heavy traffic away from the approach paths would definitely get noticed.
Even the fly-by-wire Airbus can be flown manually using differential thrust and/or pitch trim control.
The only time I've heard of an Airbus loosing control of a damaged engine is when the electrical cable was physically severed. This was Qantas QF32 [1], after one engine exploded and damaged the cables to another engine.
To "take over" an aircraft with pilots in the cockpit, would require the compromise to multiple systems.
[0] https://en.wikipedia.org/wiki/Traffic_collision_avoidance_sy...
[1] https://en.wikipedia.org/wiki/Standard_terminal_arrival_rout...
[2] https://en.wikipedia.org/wiki/Standard_instrument_departure_...
Google cars have the Big Red Button, which shuts off self-driving system and brings the car to a stop.
What more controls do you need?
Urmson talks about it here: https://youtu.be/Uj-rK8V-rik?t=14m3s
It won't matter if all the other cars on the road besides yours don't have controls.
On the other hand on EFI car, having mechanical throttle cable does not add much to hack-safety as the ECU always has some way to override closed throttle (either disengaging throttle pedal mechanically switches the control of throttle to ECU operated servo or there is completely separate throttle controlled by ECU).
I would imagine that any pilot would figure out what was going on, unless it was on an incredibly foggy day.
Although looking at the other comments, I think I'm significantly underestimating just how much of modern airliners is dependent on software. The pilots might be able to see that they're heading for disaster, but may not be able to do anything about it.
There is an idea of triple channel autolanding, wherein the plane uses the consensus of the three autolanding systems. Should no consensus be available, then the pilot is advised that autolanding is not available.
Other than that, any sourcing from different manufacturers is happenstance. 737 avionics are sourced from a different vendor than 747/757/767/777. And different functions can come from different vendors, although vendor consolidation has cut down on that.
I'm not across what happened post 777, as I left Boeing in 1999.
A related scenario, one that theoretically could happen today, is hacking into commercial airliners auto-pilot systems, and directing dozens of flights onto a target.
Set aside the fantasy movie plot angle, how realistic is this today? Is it any more or less plausible than the millions of cars scenario? If people are truly concerned about the car scenario, shouldn't they be worrying about the aircraft scenario?