Paul kgyy wrote:

If empennage elimination is such an "obvious" improvement, how come
it's taking so long?

In the case of passenger aircraft, the problem with a Jack Northrop
style flying wing (as opposed to a Sonic Cruiser style blended thing)
has much more to do with passenger comfort than technical issues.

The long aluminum tube places all of the passengers close to the
longitudinal axis, so that relative displacement of the passenger
compartment in roll is small. The opposite is true of a flying wing
design, so you end up with crap sliding off seat back trays, drinks
spilling and other passenger-unfriendly annoyances. Then there's the
distinct lack of windows, which also turns out to be an issue.

Flying wings are great for freight (including the explosive sort), but
not so hot for people.

I'm guessing that controllability is the major problem, and developers
are trying to fix that with electronic control systems?

Nah. Jack figured this out a long time ago, although computers have
allowed control systems to become even more clever.