Plain English Meaning

The safe gap that controllers keep between aircraft flying on instrument flight plans, since those pilots may be in cloud or otherwise unable to see and avoid each other on their own.

Full Definition

The standard spacing that air traffic control (ATC) maintains between aircraft operating under Instrument Flight Rules (IFR), using prescribed minimum distances or altitude differences to keep aircraft safely apart when pilots cannot rely on seeing other traffic.

Context Anchor

Seen when an IFR flight is being cleared through, around, or near an active military operations area.

Derivation

IFR stands for Instrument Flight Rules -- the set of rules pilots follow when flying primarily by to instruments rather than by looking outside. '' comes from the Latin separare, meaning 'to set apart.' Together: the act of setting apart from each other by a safe margin.