Recently, Newps posted:

[...] The plain simple fact of the matter is the limiting
factor is lack of runways. No amount of technology can force more
airplanes onto the runways we have now.

Isn't that somewhat dependent on the definition of "...the runways we have
now"? The problem is easily addressed by abandoning the hub system that
overburdens a few locations and barely worked when demand was low.
Alternatively, add hubs to some of the underutlilzed airports. Of course,
the airlines would probably find this to be a threat to direct service to
locations of highest demand, but from a passenger's point of view, it's
becoming more difficult to get a flight direct to very many places anyway.

Neil