What does "aerospace warning" consist of?

"Of what did this warning consist, Mr. Pak?"

"Of course, the warning can consist of sending back the pieces of someone, appropriately gift-wrapped."

General D'Hubert, beginning to wonder at what had become of the other, was taken unawares so completely that the first warning of danger consisted in the long, early-morning shadow of his enemy falling aslant on his outstretched legs.