Analysis of the August 2, 1985 crash of an L-1011 jumbo jet (DL-191), on approach to the Dallas-Ft. Worth International Airport in a thunderstorm, indicates that the severe windshear microburst which caused the crash was composed not only of a strong downflow and outflow but also included several large-scale vortex rings entrained in the flowfield. A detailed model of the microburst, based on data from DL-191, is presented. The model uses wind vector and flight path data reconstructed by NASA-Ames Research Center from the digital flight data records and ground-based radar measurements. The model was developed using a combination of interactive graphics and a least-square-error best fit between the modeled and measured wind vectors along the DL-191 flight path. The model confirms a microburst structure based on a von Karman vortex street, and indicates that the L-1011 flew near or directly through several strong vortices. In addition, the results also confirm that the reconstructed wind vector data contain a time lag of about 3 s in the horizontal winds. >