Fly-by-wire is a term applied to rocket-type weapons that permit the user to manually steer and control the rocket, deciding where it goes, the speed at which it flies, and when it detonates (either detonation by impact or a set explosion by pressing the fire button).
Found in the Level Skedar Ruins for Perfect Dark. When a Gameshark code, or built in menu cheat is enabled, the Fly-by-wire will only be found in the levels in which the Skedar are the main enemy, Attack Ship and Skedar Ruins. If the Fly-by-wire rocket is flown too high up in the levels, connection with the pilot will be lost.
This fire mode was seen in Perfect Dark Zero with the Rocket Launcher, therefore dropping the Targeted Rocket function, and made a subseqent appearance in Perfect Dark in the form of the Slayer rocket launcher.