aeronautics air lane air route air service airway astronautics aviation axis ballooning beeline blind flying chord cloud-seeding commercial aviation contact flying corridor cruising cut cutoff diagonal diameter direct line directrix edge flight flying general aviation gliding great-circle course lane normal path perpendicular pilotage radius radius vector right line sailing sailplaning secant segment shortcut shortest way side soaring straight straight course straight line straight stretch straightaway streamline tangent transversal vector winging