An autothrottle is necessary to advance safety because the autopilots are now so good in lateral and vertical control. It doesn't take long to develop so much confidence in a fully capable autopilot system that you find yourself looking away from the primary flight instruments to perform other chores, such as dial radios, look at charts, read checklists and so on, while the autopilot maneuvers on course. The system makes its course and altitude changes with such precision and dependability that we all soon take it for granted. But in all but a few business jets we, the human pilots, must still be paying very close attention to the airspeed as the airplane turns, descends and levels off. And airspeed control is at least as important, actually even more so, than being exactly on course and altitude.