[BiggBob]

Wheels up is generally an aviation term
For after the aircraft has left the ground and the wheels are retracted for flight

So in sticking with the B2 posts

I’m guessing wheels up implies the stealth bomber is in the air and in the way to drop its payload

[SteveH]

technically, the expression “wheels up” can also refer to belly landings. It means that that the wheels are retracted.

[TangoLimaSierra]

Wheels up is generally an aviation term
For after the aircraft has left the ground and the wheels are retracted for flight
So in sticking with the B2 posts

Evidently the first B1 test-flight was wheels down throughout the flight.

I take the "Wheels up" to mean this is not a test. It's for reals.