Subsolar stand-off distances of bow shocks from previous cometary flyby missions as well as from simulations of solar wind-comet interactions. The black symbols show spacecraft-measured distances, and the coloured symbols show simulations. The models of Biermann et al. (1967; dashed line) and Koenders et al. (2013; solid line) are also included, with nominal solar parameter values at 1 AU (n_sw = 5 cm^-3 u_sw = 400kms^-1, v = 7 × 10^-7 s^-1, and u_n = 1 kms^-1). The grey shaded region indicates a change of a factor of two (up and down) in the solar wind dynamic pressure.