I would echo much of what has been said so far, and I think we shall never see domestic air travel return to previous levels - except perhaps to/from Northern Ireland.
For people who routinely used domestic flights, a large amount of working from home will be a permanent 'new normal'. And with that, these same people have now realised what a complete faff it was to get up at some ungodly hour of the night/morning, and drive in the freezing rain to an airport, hang-around and grab a tasteless luke-warm beverage (is this a coffee, or just the wastewater from the dishwasher?), possibly queue to get on a hot stuffy bus to be taken the remote area where the turbo-props are hidden from public gaze, endure an hour or more of tooth-rattling vibration, followed by the frustration of finding the booked hire car is not available, and has been substituted with some tinny contraption resembling a cartoon car with all the power of an asthmatic donkey, through which one has to do battle with heavy traffic on the way to the client all for a two-hour meeting.
Rinse and repeat in reverse on the way home. I know, I've done it hundreds of times!
Thank goodness those days have ended - and I, and my colleagues, hope we never have to endure this utter waste of time again.