There are many different kinds of competition for control line model airplanes. The prevailing four main categories in the Toronto, Canada area are Combat, Stunt, Scale, and Racing.
Two control-line airplane pilots stand in the same circle. Each of their airplanes is equipped with a trailing streamer. They fly simultaneously, each pilot trying to score points by cutting the other pilot's streamer. Collision carnage is frequent, and pilots earn extra points for staying in the air! Judging is primarily quantitative.
Contestants fly individually. They are required to fly an aerobatic "pattern" of manoeuvres, scoring points for the gracefulness of each manoeuvre. Judging is primarily qualitative.
Aircraft are built "to scale" to resemble a "real" aircraft. The aircraft must also fly. Points are awarded for both static appearance and flight. Judging is primarily qualitative.
The first plane across the "finish line" (a set number of laps) wins. There is usually two or three pilots flying simultaneously in the same circle, and at least one pit stop is usually required. Judging is primarily quantitative.