Left: absolute bolometric magnitudes M_bol versus flux-weighted gravity g_F of Galactic blue supergiants are plotted with error bars. For most of the stars, Gaia DR2 parallaxes (Gaia Collaboration 2018) are used. A blue line indicates the mean relation of LMC blue supergiants obtained by Urbaneja et al. (2017). The blue dashed line labelled G2_b corresponds to the relation log L/L_⊙ = 3log M/M_⊙ + 2.03 (Meynet et al. 2015b), which gives the lower bound of the FGLR for the BSGs of Local Group galaxies. Right: blue parts (log T_eff >  3.9) of evolutionary tracks with various parameters are compared. The labels ‘S0’ and ‘S4’ refer to models with an initial rotation rate of 0 and 0.4 of the critical one, respectively. Some Galactic LBVs are shown by filled blue squares. The loci on the g_F − M_bol diagram clearly indicate that significant mass losses have occurred in LBVs.