Abstract: A close formation flight positioning system uses only air data measurements without a data link. The wake vortex of a lead aircraft generates horizontal, vertical and lateral induced velocities that vary with horizontal, vertical and lateral position from its wing. Two or more laterally or vertically separated air data sensors on a follower aircraft measure impact pressure, angle of attack and angle of sideslip, which are converted to horizontal, vertical and lateral velocity components. By comparing these velocity component measurements, using the distance between the sensors on the follower aircraft and the wing span of the lead aircraft, the distance from the follower to the lead aircraft can be determined. If weight, speed and altitude of the lead aircraft are known, then two sensors on the follower aircraft are sufficient to determine relative positions. If those conditions are not known, then three sensors on the follower aircraft are needed.