Definition
An instrument approach procedure that allows two aircraft to fly approaches at the same time to closely spaced parallel runways whose centerlines are too close together for standard simultaneous parallel approaches. One aircraft flies a straight-in ILS or RNAV approach to one runway, while the other flies an offset approach (typically an LDA with glideslope or an offset RNAV) angled 2.5 to 3 degrees away from the first runway's final approach course. The offset keeps the aircraft laterally separated until the trailing aircraft breaks off visually and sidesteps to land on its own runway.
Plain English
A way of running two approaches into two close-together parallel runways at the same time. One plane flies straight in. The other flies a slightly angled approach so the two aircraft stay safely apart, then visually lines up with its own runway near the end.
Context Anchor
Seen on approach charts and in instrument approach briefings at airports with closely spaced parallel runways.
Derivation
Simultaneous (at the same time) + Offset (angled away from a reference line) + Instrument Approach. The name describes the operation directly: two approaches running together, with one offset from the other to maintain separation.
Why Pilots Care
It raises airport arrival capacity while preserving safe separation between aircraft on parallel approaches.
Grounding Statement
Picture two airplanes approaching two nearby parallel runways at the same time, with one airplane on a straight path and the other on a slightly angled path until it can safely line up visually.
Intuition Check
Do not assume a SOIA procedure is just two normal approaches happening side by side. The offset path and the required visual check near the end are what make it a SOIA procedure.
Example Sentence 1
Cleared for the SOIA LDA Runway 28L approach, the crew briefed the 2.5-degree offset and the visual segment required to line up with the runway.
Example Sentence 2
During SOIA operations the pilot monitored the adjacent approach path to maintain required separation from the other aircraft.