Definition
A procedure that allows simultaneous instrument approaches to two parallel runways spaced less than 3,000 feet but at least 750 feet apart. One runway uses a straight-in ILS or equivalent precision approach, while the other uses an offset approach (typically an LDA with glideslope) angled a few degrees away from the parallel runway centerline. The offset reduces the risk of collision if one aircraft strays toward the other, and visual separation is required for the final segment.
Plain English
SOIA lets two aircraft land at the same time on closely spaced parallel runways by sending one straight in and the other on a slightly angled approach, so their paths don't line up directly next to each other. Once close to the airport, the pilot on the angled approach must see the other aircraft and the runway to continue.
Context Anchor
You may see SOIA in approach procedures, airport arrival planning, and air traffic control clearances at airports with closely spaced parallel runways.
Derivation
Offset' means shifted or angled away from a reference line. Here, one approach path is intentionally angled away from the other runway's centerline so the two arriving aircraft are not flying side by side on identical tracks.
Why Pilots Care
It increases the number of arrivals an airport can handle during busy periods while preserving safety through strict lateral spacing rules.
Analogy
It is like two cars entering side-by-side lanes where one lane is angled slightly away at first, giving both drivers more room before the lanes straighten out near the end.
Intuition Check
Do not read “offset” as a casual correction or a small drift from course. In SOIA, “offset” means the approach path is intentionally designed at an angle to help keep aircraft separated.
Example Sentence 1
When arriving at SFO during good weather, expect a SOIA approach to runway 28R while another aircraft is cleared straight-in to 28L.
Example Sentence 2
During the SOIA arrival the crew on the offset leg called the runway in sight at the published visual descent point and continued to land.