they're a pretty big fraction for shorter range flights/smaller planes (somewhere around 10%?), and more importantly they are a cause of cascading delays. often major delay problems happen because the flight before was delayed requiring the pilots to stop working and you now need to reschedule all your pilots leading to more problems. pilots are more of a problem than flight attendants because there are more attendants, so you can more easily have a few in reserve.

Pilots are more of a problem than flight attendants because not only are there fewer pilots, they need to be certified for the plane you have available. If your reserve pilot is certified on a CRJ-900 and you need to fly a 737, those folks aren't going anywhere.

>We'll have terrible Roomba boxes replacing flight attendants long before anything replaces pilots.

For American-run airlines (and many European ones too), terrible Roomba-like boxes would be a big improvement in service.

Not for Asian airlines, though.

Not sure about the replacements for flight attendants. I understand they have important tasks during emergencies.