How exactly does a pilot engage the autopilot?
“One Switch” to operate the Autopilot is not true. That’s just the movies.

Autopilot systems vary in each aircraft. Larger jets have it divided into two: Auto-Throttle and Auto-Pilot. Smaller aircraft/piston aircraft don’t really have auto-throttle capabilities.

The Autopilot is not just to “maintain” current flight path. It really can fly the entire flight from take-off to touchdown. This includes flying a departure procedure, en-route navigation, arrival procedure, an approach and touchdown. 

Theoretically, it is possible for a pilot to not touch the aircraft controls (yoke/stick/throttle) after liftoff all the way until touchdown even if the mission is a complex IFR flight. Realistically, pilots love to fly and they will fly.

Many settings exist for each autopilot system, and these include (but are not limited to):

Lateral Navigation


Heading Mode (fly the “selected” heading”)
Nav Mode (fly the “selected” nav course)
Roll Mode


Vertical Navigation


Altitude Select Mode (Maintain the selected altitude)
Vertical Descent with a fixed speed
Vertical Descent with a fixed rate
Approch Mode (Vertical Descent with Glideslope)


Auto-Throttle


Maintain Selected Airspeed
Accelerate/Decelerate to Selected Airspeed


However, there is that master AP Switch that’ll disable all things related to the AP.