Trajectory is the direction the loop travels relative to the horizon. It decides how far the fly has to fall once the loop opens, and that fall is where accuracy is easiest to lose, so choose the trajectory for the target and the conditions.

To bring the loop in low over a close target, tilt the casting arc so the rod tip path aims down at it; the line and leader then unroll much closer and the fly has a short fall. How steep the pitch is depends on distance:

• Short casts (20 ft): a steep pitch, up in back and down in front.
• Long casts (45 ft): a shallower pitch.

A flat trajectory is not automatically inaccurate. It keeps the loop travelling level, it is efficient, and it is the right answer when the target sits at that level; what costs accuracy is arriving high over a close target and leaving a long fall for wind to work on. The fly leg goes where the rod tip path points, so change the trajectory by changing the orientation of the casting arc.

Tasks 12 and 13 ask for 20, 30 and 45 ft targets, and each distance needs its own trajectory rather than one memorised pitch for all three. Loop control matters too: the guide ties straight fly legs to the most accurate loops.

Source

From the CI Study Guide (2025) (PDF), “Varying Casting Arc and Trajectory” and Tasks 12–13; terms from the FFI Fly Casting Definitions (Trajectory).