I sent my own letter. I thought the ALPA letter was weak on why two pilots were preferable.
I highlighted:
1. Radar interpretation/turbulence prediction (generally both confer; and automated products like WSI are often wrong). Sometimes, it is a combination of WSI, on-board radar, visual, and experience that finds the best path.
2. Mental alertness. Long haul at night is tough. How do you fight it? Best thing I’ve seen is conversation with the guy next to you. I doubt that would happen with a remote copilot.
3. Mechanical failures. Sure, drones fly just fine...including autoland...when everything works. What about (example) airplanes like the 767 that can’t autoland single-engine? What if it DID have single-engine autoland, but part of the system dumps...or is MEL’d?
4. Datalink reliability. Never seen one yet that was impervious to failure. For that matter, what about hacking, or viruses?
5. Sudden incapacitation. About one pilot a year dies in flight on a US carrier. Now you are totally dependent on the remote sytem and autopilot.
6. The argument that trains, elevators, and now cars can be driven autonomously ignores the most important facet: in event of failure, they can STOP.
Planes....not so much.