The problem of plume-forming meteoroid impacts into the Earth's atmosphere is investigated with the use of a simplified analytical model and detailed numerical simulations. The process of plume formation is found to depend strongly on the meteoroid size due to development of Kelvin-Helmholtz instabilities at the entry column boundary. As a result, the height of plume rising proves to be considerably less than that obtained using simplified model or numerical simulations with low spatial resolution. It is shown that meteoroids several meters or less in size do not create ballistic plumes at all. The results of general consideration are applied to the Šumava bolide (one of the brightest detected by the European Fireball Network). The debris cloud created by this impact rises to an altitude of about 190 km. ¿ 1999 American Geophysical Union