Planetary nebulae (PNe) can be used to probe the dynamics of a galaxy at a large distance from its centre. Romanowsky et al. (2003) reported the dynamics of three luminous elliptical galaxies up to 6 effective radii can be explained by Newtonian dynamics without dark matter. This can also be understood in the framework of MOND (MOdified Newtonian dynamics), because the high acceleration of the systems implies small acceleration discrepancy between Newtonian dynamics and MOND (or equivalently, the mass discrepancy is small). In this contribution, we revisit this problem and use all available data from the literature. There are six elliptical galaxies with PNe data up to 6-8 effective radii. We conclude that MOND can explain the dynamics of all these galaxies well.