"In the Air Force we have a rule: check six. A guy is flying along, looking in all directions, and feeling very safe. Another guy flies up behind him ( at "6 o'clock"-"12 o'clock" is directly in front) and shoots. Most airplanes are shot down that way. Thinking that you're safe is very dangerous! Somewhere there is a weakness you've got to find. You must always check six o'clock.
- US Air Force General Donald Kutyna