It also employs tens of thousands of our nation's best and brightest engineers..
Who are unavailable for other tasks due to this programm.
and almost all of it goes to labor (and a big chunk returns in taxes, if not all in economic activity)
As would almost any other type of spending. The difference is, you get planes instead of schools, highways, vaccines or what else could be done with the money.
Also, the money for this programm is coming from taxes so not spending the money at all creates purchasing power all accross the population which might be the best thing for welfare and economy.