The U.S. Federal Aviation Administration's (FAA) Instrument Flying Handbook defines IFR as: "Rules and regulations established by the FAA to govern flight under conditions in which flight by outside visual reference is not safe.
Den amerikanske flyveadministrations Instrument Flying Handbook (Instrument Flyvehåndbog) definerer IFR som: "Regler og reguleringer fastsat af FAA for at regulere flyvning under betingelser, hvor flyvning uden visuelle henvisninger ikke er sikre.