When an aircraft flying at a constant airspeed performs circular orbits relative to the ground, its path relative to the air has interesting features if a wind of uniform velocity is blowing. The locus, which is here called an aeroid, bears some resemblance to a prolate trochoid; its equation is obtained in parametric and intrinsic forms, and its curvature and other fundamental properties are derived.

In the final section of the paper some practical implications are considered, including the effect of wind on the fuel consumption per orbit of a circling aircraft and the influence of winds of different headings on the path for a landing approach.