Abstract: A mechanism for linearizing an open, vertically directed, high-speed air flow, generated by a propeller rotating about a vertical axis, includes a vertical cylindrical element mounted above and coaxially with the rotating propeller and a plurality of radially oriented vertically planar guide vanes supported at their radially outside ends in such a manner that ambient air can flow radially inward below and above the propeller. For large cross-section air-flows and improved elimination of swirl components from the flow, a second set of shorter radial guide vanes is provided in alternation with the vanes that are connected to the cylindrical element. A net structure is disposed above the guide vane structure for use of the invention in a system for producing a relatively large cross-section linearized flow to enable free-fall simulation exercises by one or more participants, to enable trainers to stand close to the free-falling participants.