A pennant is a tapered flag. IIRC if you steal a sheep you might see a pennant over your aircraft indicating sheep on board.
There used to be a capture the Flag game for AH. You flew into an enemy field through their pennant and it attached to your plane. Then you tried to runaway with back to the nearest friendly field while being chased and shot at by the owners of the flag.
That sounds like fun. Is this something we can still do in the training arena, or in a custom arena?