Actually, its quite a common manuever to pull off. The
zero-g-push over can be done at any altitude. For whatever
reasons.
For a fighter. Climbing to 40k ft, then executing a zero-g-pushover
is used to get thru the transonic region (between mach 0.7 - mach
1.2) quickly. In this region, the wave drag increases
substantially, but once passed into the supersonic speeds, it
decreases again. Hence a manuever like that is really just to make
sure u don't burn too much fuel trying to get supersonic.
Of course, planes like the F/A-22 probably wont have to do that
since it almost flies clean (internal weapons stores), and has a
kickass F119 engine to begin with. Each F119 is capable of 35000lbs
of thrust, which is a total of 70000lbs of thrust! More than twice
the power that pushes an F-16!
