what is: "construction crews" and "flyby castings"

[JJ_Colorado]

Hi,

Norfleet wrote in another post that he killed entire armies by turn 22 of a game using "construction crews" and "flyby castings".

What do these terms mean? I could take wild and probably wrong guesses:

construction crew: death mage crew that summons hordes of undead during a battle?

flyby castings: mages who cloud trapeze in, use ritual of returning, storm staff, and cast wrathful skies?

I know these guesses are probably wrong. Can someone clue me in?

Thanks,
John