OK – let’s clear up a couple of misconceptions before we do this..
#1 ) Misconception 1 -We do NOT “need’ ATC. In fact most airports in the USA are uncontrolled. In yet others the control towers operate only part time. The job of an “air traffic controller” is to MAINTAIN SEPARATION FOR AIRCRAFT OPERATING UNDER IFR FLIGHT PLANS. Their secondary duty is to “Facilitate and smooth the flow of air traffic”. I have flown literally thousands of flights in my personal aircraft which began and ended without ANY contact with anyone in any ATC facility anywhere, and the same holds true for almost all pilots. Now ATC provides a valuable service. They are nice to have. They can be handy in an emergency. They do a tough job and for the most part they do it well BUT the general public does NOT understand their actual role in aviation. If every air traffic control tower went silent at the same time – every flight in the air can and would land safely without them. It would just revert to a system of “self announce” and use your mark II eyeballs to spot and maintain separation from traffic.
Misconception #2 – A co-pilot doesn’t exist. There is a captain and a first officer. The captain is in charge, the first officer is essentially a captain in training. BOTH individuals hole Airline Transport Pilot licenses, both are fully type rated in the aircraft. Either is equally capable of flying the aircraft – one has just been upgraded to captain because he has the seniority to hold the position and thus draw the higher pay for the greater responsibility. One could say ALL airline pilots are hired as “future captains” ie you interview to be a captain, you are hired as a first officer. Flying skill does not enter into the difference between a captain and a FO. In fact, when I became a captain on the 777 I routinely flew with First Officers who knew more about that aircraft and had substantially more time in it than me. Either pilot is the equal of the other in terms of flying ability and either could land the plane without help.
Now this said -in an airline environment the Captain and the First Officer usually switch off legs and are described by the checklist not as pilot / copilot but Pilot Flying and Pilot Not Flying. On any given leg the pilot flying may be the captain or the first officer and they land the plane. The pilot not flying does the things called for in the checklist as duties for PNF – for example the checklist itself, radio calls and frequency changes, etc. There are a few situations where it has to be the captain, for example an emergency. (If you recall Sykes was flying and sully was not flying. Once they had the bird strike Sully took over. There are some airports or weather minimums or crosswinds or so forth where individual airlines may dictate the captain be the operator of the controls but on almost every leg we switch between PNF or PF.