A co-pilot is a buddy who you would take with you while on the prowl for chicks. Co-pilots are generally the substitute for a wingman when one is not available. A common use for a co-pilot is to distract her friends while you make your move. However, a co-pilot can't be granted the same level of trust as a wingman, in the sense that they are usually rookies and have yet to earn their wings. Therfore, co-pilots are a last resort.
Guy 1 - "hey man, I need a wingman for tongiht. You in?"
Guy 2 - "Sorry dude, I have to work early in the morning. Why don't you get your little bro to co-pilot you?