Final answer:
The command 'Order arms' is given to execute the second count of the hand salute, where the hand is brought down from the salute position in a uniform manner among airmen.
Step-by-step explanation:
To execute the second count of the hand salute in the Air Force, the correct command that should be given is Order arms. The sequence of commands for a hand salute generally begins with the command 'Present arms', which is the first count where the hand is brought up to the correct position. The second count involves the command 'Order arms', where the hand is brought down from the salute position to the side of the body. This is essential to ensure uniformity and discipline among the airmen as they are taught to walk, move, and look like each other during their basic training.