When I speak of a co-worker, or a co-driver, I'm speaking of a mutual relationship and status (that's simply how the prefix co works in normal English) and I'm pretty sure it's what most people mean too.
When people speak about co-pilots on the other hand, it seems they might mean one of several things:
- They are speaking of two pilots who happen to be working as part of the same crew, who are therefore co-pilots (which seems the most correct usage).
- They mean a pilot who isn't the captain.
- They mean the pilot monitoring rather than the pilot flying.
- They think the aircraft has a pilot, and a kind of assistant pilot of lesser abilities known as a co-pilot.
(This last seems to be strangely prevalent, as if people imagine an airliner might be crewed by a fully-qualified professional and by some sort of assistant whose job is the aviation equivalent of holding the ladder, who looks forward to the day they'll be allowed to climb up it themselves.)
Weirdly, I have actually heard air crews use co-pilot in ambiguous ways, as though even they have given up trying to use the word with care; once I heard an announcement in one language that referred to the captain and the first officer, and then immediately afterwards in another to pilot and co-pilot.
Questions about co-pilot
It seems reasonable to say "my co-pilot" when speaking of a fellow crew member. However:
- Does "the co-pilot" have any meaning (note the use of the definite article)?
- Is co-pilot ever a rank?
- Does the term appear in aviation regulations?
- Is it used in crew management policies?
- Is there indeed any standardised or formal use of it within the industry?