That’s true, but there are plenty of other options. For example, a dead-man switch could:
Send an alert via transponders that it has been activated.
Maintain level flight but avoid terrain. (After a waiting period in which a pilot can deactivate this feature.) Or descend to a safe altitude if cabin pressure is lost.
Activate a mode in which the plane could be remotely flown or directed to land itself.
Alert flight crew that the pilots are incapacitated.
Or the most basic: make some noise to wake up the pilots.
The existing action is to maintain current settings. A flight in Australia flew across the continent that way, after (theory says) somehow depressurizing during takeoff so everyone passed out.
IMO that story shows that unless you do the remote control option (which I see as unlikely) it doesn't matter what happens...what can anyone outside the plane do except crash it earlier?
>That’s true, but there are plenty of other options.
Well we can't settle it in the comments, nor should we. So which of those options can successfully survive a detailed engineering review on its merits?
> Not having anyone flying the plane when it is on manual control can also kill people
Not as quickly. Routes are programmed into an airliner before takeoff. Those routes are planned with emergency landing in mind. Left to its own devices, a plane flying its flight path is safer than one simply holding FL (while avoiding terrain).
I recall reading that certain aircraft manufacturers do offer more robust security features if the airlines are willing to pay for them. I don't have a link or source handy, but it's entirely possible that these features have been discussed, but through the lens of how much more would it cost to implement them.
Send an alert via transponders that it has been activated.
Maintain level flight but avoid terrain. (After a waiting period in which a pilot can deactivate this feature.) Or descend to a safe altitude if cabin pressure is lost.
Activate a mode in which the plane could be remotely flown or directed to land itself.
Alert flight crew that the pilots are incapacitated.
Or the most basic: make some noise to wake up the pilots.