Definition
The point at which a new system, in this context the Wide Area Augmentation System (WAAS), has been certified and approved for use in the National Airspace System, allowing pilots to begin using it for navigation and approaches under published procedures.
Plain English
The official moment a new system is declared ready and approved for pilots to actually use in flight.
Context Anchor
Seen in FAA discussions of WAAS and GPS-based procedures when describing when a navigation service first became available for use.
Derivation
From Latin 'initium' meaning 'beginning' and 'operari' meaning 'to work.' Together the phrase means 'first point at which the system is working well enough to be used.' It marks the start of real-world service, not the end of development.
Why Pilots Care
It establishes the legal starting date when certain GPS-based instrument procedures can be flown and when operators may begin training and equipping for them.
Intuition Check
IOC does not mean the system is unfinished and unusable. It means the first approved, usable level of the system is available, with possible improvements still to come.
Example Sentence 1
WAAS reached initial operational capability in July 2003, allowing pilots to begin flying LNAV/VNAV and LPV approaches.
Example Sentence 2
Operators waited for IOC before submitting approval requests for WAAS approaches at their home airports.