What is an autopilot?

Answer 1

When flying an airplane, the most common practice is to take off, climb to a certain altitude, point the aircraft at the destination, and then wait.

It may take several hours for the aircraft to reach its destination, and it is not necessary or desirable to require the pilot to constantly maintain the aircrafts heading and altitude manually. To this end, many aircraft are equipped with autopilots which can be set to automate much of the intermediate flight. This frees the pilot for other duties such as navigation, communication with ATC, and various system checks while also reducing pilot workload and fatigue.

Modern autopilots can be very sophisticated, also controlling the engine thrust and other vital components, they may also tie into the aircraft flight computer to automatically fly complex approach patterns and even land the plane.

None of this altogether eliminates the necessity of having a skilled and trained pilot in the cockpit, and there is no serious talk of making the system completely automated, indeed FAA regulations specifically forbid un-piloted aircraft from carrying passengers. However, these systems do go a long way to taking the guess work out of flying large aircraft, and are vital to the modern aviation industry.