The big one?
Any business trip that would be cheaper served with Zoom or Skype will be zoomed or skyped.
Lots of companies have figured that out now.
Yes. People are used to working from home. Those who can will continue to do so.
The business market will definitely be affected in perpetuity even after the crisis has abated. Such trips will be less in frequency and volume, and even though airlines are trying to reach out (all but one of the carriers I use has sent several messages) that is unlikely to be sufficient for most. Even if they gave cheaper corporate rates, cheaper is still more expenses than zero cost (and that is not considering that flights also mean hotel and other related costs).
Unfortunately for the airline industry, there will be an overhang of business travel that simply will not be coming back. It may only be 20-30% that is not coming back, but that 20-30% will have an impact on their bottom line.