Or even better. A device capable of sending that distress signal automatically without any intervention of the crew. It's not difficult to automatically detect emergency situations based on the different sensor readings available in a commercial plane.

A similar solution could also be applicable to other means of transport. E.g. A similar solution would have been extremely useful for the indonesian submarine lost weeks ago.

All such systems will have overrides (imagine the "HERE I AM EVERYONE!" beacon triggering on the submarine when it's hiding as part of its primary, military, job). On an aircraft there is almost no powered circuit without a breaker to enable the crew to shut it down if malfunctions, or worse yet catches fire. So a crew that has prepared properly will still be able to go dark.

Which is one of the elements of MH370 that suggests a deliberate act: it did go almost entirely dark, but for the hourly satellite pings. If the flight recorders are ever found then it may be learned if this was so, and whether it was malfeasance or part of a lost fight against malfunctions/fire.

> On an aircraft there is almost no powered circuit without a breaker to enable the crew to shut it down if malfunctions, or worse yet catches fire. So a crew that has prepared properly will still be able to go dark.

I think "crew" is the key part here, right? I understand a system like this would be designed in such a way a single crew member could not make a plane go dark -- or make it stay dark after disabling the safety systems. For example, a rogue pilot can manage to turn the beacons off, but any other from the cabin crew can just turn it on again while the pilot is in the cockpit, etc.

I still need to find out which changes this even brought to the entire airline ecosystem.

But what good would that do? Alerting the police or even the air force is not going to allow them to board the plane in flight to take back control. It wouldn't have helped in this case. Only a full remote override capability would and that's also a security risk in itself.

Giving a flight attendant a backdoor code would make them more susceptible to a hostage situation.. It's one of those damned if you do, damned if you don't situations I guess. There is no perfect answer in the situation where the most trusted person is compromised without compromising security in all the other scenarios.