These days a commercial aircraft is flown by a two-person crew consisting of a pilot and a first officer. The pilot is often referred to as the ‘captain.’ The first officer is sometimes called the ‘copilot.’ A few older model aircraft that are still in service, like the Boeing 727, require a third pilot called the second officer or ‘flight engineer.’
Both the pilot and first officer are fully qualified to fly the plane at all times, but the pilot or ‘captain’ always has ultimate authority over the flight. On long distance routes both of the crew will alternate command. If a flight is going from New York to Dallas to Los Angeles, the captain will fly the first leg and the first officer will fly the second leg.
The pilot who is not flying is still busy - however - working the communication radios and navigational computers. If there is one word that distinguishes these two officers – it is “seniority.”
Before a flight, the crew examines the airplane's control equipment, checking each item off on a list. After determining the weather and flight conditions, the flight plans are approved by the air traffic controllers. The copilot charts the airplane's route and computes the flying time. By radio the captain then requests that the aircraft dispatcher give permission for them to taxi to the runway. After receiving clearance for takeoff, the pilots accelerate the plane down the runway until the plane lifts off and is airborne.
Once the plane is in the air, it usually flies by itself on automatic pilot. The pilot and co-pilot regularly report to air-route control stations by radio, reporting any problems they may be experiencing. They receive information about the weather and any traffic in their part of the sky. Near their destination airport, the captain rechecks the landing gear and requests clearance to land from the air traffic controllers. After landing, the pilots must file a flight report. Then the plane is turned over to the maintenance crew.
The captain normally wears four uniform stripes and the first officer wears three.