At this point, whenever there is an incident with neurology-related crew incapacitation or degradation (cf. the Jeju air disaster and how many professional pilots fail to make sense of crew’s actions) and the aircraft uses bleed air, I am donning tinfoil and suspecting a fume event.

For a mind-boggling near miss account (actually, not even a miss, since one of the crew has died in the aftermath), see https://avherald.com/h?article=4b6eb830. It quotes research estimating that in the US alone the number of air fume events is around 2000 per year, while the number of reported fume events is less than 10. Mental degradation is insidious, because you may not even be aware it is happening in the first place, so if you have arrived safely you have nothing to report. Yet the industry is silent (including FAA, which had no record of the Spirit incident).

It should be straightforward to mandate a subsystem that presents mental challenges to pilots to test their awareness, and that simplifies access (e.g., disables the emergency override timeout that apparently slowed down the entry in the Lufthansa incident) if one pilot is out to pee and the one remaining is not responsive.

I am curious if pilots in Spirit and Lufthansa cases exhibit similar neuro-degenerative damage.

Maybe ditch the pilots. Autopilots can taxi, take off, cruise, respond to tower instructions, land. And aren't (as) affected by fume events.

Why put a weak link in the safety chain? Humans are so very fallible. Arguably more so than an autopilot.

Lufthansa at it again. Wasn't there a rule after the Germanwings Flight 9525 crash that one member of the cabin crew has to replace either one of the captain or the first officer when one of them temporarily leaves the cabin?

Reminder some flight companies are trying to get rid of the 2 pilot requirement.

As seen here, It absolutely wouldn't work.

Safety first and foremost.