Plain English Meaning

Flying when you can't see outside well enough to use the horizon or ground for reference, so you fly the airplane entirely by what the instruments tell you.

Full Definition

Flight conducted in weather conditions that require the pilot to control the aircraft solely by reference to the flight instruments rather than by visual reference to the ground or horizon. It involves operating in or near clouds, low visibility, or other conditions below visual flight rules minimums, using instrument indications to maintain attitude, , and .