Andrew Sarangan wrote:

Most of the software out there will compute a flight based on the
user's route, time of departure and altitude. This is a fairly
straight forward task which could be done without a computer, as has
been the case for decades.

What I am looking for is the reverse. Given a destination, aircraft
type and a window of travel time (which could be a couple of days),
the software should come up with the best altitude, route and time of
departure. It should consider forecasted winds aloft, frontal
positions, icing potentials, turbulence and thunderstorms. The user
should be able to attach numeric weights to indicate the level of
importance to each factor. In other words, it should be a minimization
software considering a variety of decision matrix. At present I do
this by recomputing the flight for each scenario. This does get very
cumbersome, and is best done with an automated algorithm. If such a
thing exists, I would like to hear opinions.

There is something out there that does lots of this, but I don't think it's
available at the single user, spam-can level. Essentially, it's the
classic knapsack algorithm. You can choose to optimize for minimum
fuel or minimum time. It does routing based on weather and other factors
such as TFRs, etc. However it assumes you tell it either departure or
arrival time & location. AFAIK there's no way for the software to
provide the optimum without one of the inputs.