Flight shapes: spiral descents and circling tracks

Most flights go more or less straight from one place to another. Some tracks circle instead, and the circles that become stories here lose height as they turn: an aircraft spiraling down over one area. Pilots practice steep spirals in training, and skydiving aircraft often spiral down after a drop.

The site measures each shape from the saved positions. It counts closed loops from the turning that adds up to a full circle and allows for wind drift. A spiral descent needs that verified circling, a loss of at least 1,500 ft and a track that descends through most of its reports. Loops close to a runway at low altitude are routine traffic around an airport and do not count. Single circles, repeated passes, long loiters and sharp course reversals are measured too; they add context to other stories and do not get stories of their own.

A shape does not tell you why an aircraft flew it. A descending circle can be training, a jump plane coming back down or a pilot losing height before landing, and the record cannot tell these apart. Gaps in the data can also hide part of a loop, so the counts describe the saved positions only, and the track maps show where the gaps fall.