Comparison of orbital and physical classification of fireballs using two physical classification schemes. The Tisserand parameter with respect to Jupiter is compared with the P_E parameter in panel a and with Pf in panel b. Symbol sizes and colors distinguish five intervals of meteoroid masses. Fireballs with unusual spectra are also marked. For most fireballs, however, spectra are not available. Fireballs supposed to be irons on the basis of other criteria (see Sect. 3.4) are marked by white crosses.