WFH is 'brilliant`, many say they see a significant GAIN in productivity from people.
Again, where is the evidence for these statements?
I don't imagine that there's enough shared data yet to make a call one way or the other on this matter. I'd say that certain industries and businesses, and for that matter certain personality types are finding that WFH is incredible, whilst other are experiencing the opposite in the long run. There have been many reports over the last 14 months of people working longer, or being expected to be available outside of a normal working day of an office. Whilst saving on commuting, the net gain isn't so great.
Companies will try to cut costs, that's what they do, especially the more the 'bean counters' are given hegemony over others. However, the old adage "Buy cheap, buy twice" will be needed to be adhered to and saving on an economy flight and having your staff arrive stressed and not on their best game would be a false economy compared with a business class seat on the same flight. Short haul of less than 2 hrs I suppose wouldn't make too much of a difference, though lounge access might sweeten the experience and allow work whilst waiting for the flight.